Don't know where you're getting your numbers from, but each transport costs 400-500 bcs.
The numbers are right out of the game. As I mentioned in my post, I was using a Cargo Hull, and no Miniaturization (therefore max size is 60), because that would unnecessarily complicate matters. The bigger the size, the more design options are available. Also, the cost of my design was 417bc, which fits right into your 400-500 ballpark. Not sure why you are complaining.
You need about 3000 (2500 sometimes) troops to reliably capture colonies. This means:
Cargo Hull (55 bcs)
3 Advanced Troop Modules (210 BCs)
1 Warp Engine (140 BCs)
That adds up to 405 BCs. And this is bare bones. If you want anything else, it adds to it, hence the estimate of 400-500 bcs.
First off, this design isn't possible with a size of 60. The Troop Modules alone would fill that up, leaving no room for anything else. Also, it has no Life Support Modules, which means, that the range is pretty small. Unless you are playing on a small map, where range isn't an issue, it wouldn't work. There is no point in trying to invade, if I can't reach my target. Also, as I said before, I prefer speed to troop size. Several fast Transports are preferable to a few slow ones. At least in my opinion. The slow speed only increases the chances that the enemy will catch up and destroy them.
One last thing, the most expensive Warp Drive (Mk. V) costs 100bc. I guess you meant the Hyper Warp Drive Mk. III.
Furthermore, even with 3000 troops, there's a 10-20% chance you won't capture the colony due to a bad roll or a population over 8000, which is why you need 5 transports to capture 4 colonies.
If a planet has a population of more than 8b, then send in one Transport with 1k troops, and use Mass Drivers. They won't win, but they're not supposed to. It's just to soften up the enemy. After that, you can send in the rest of the troops, and win with no to minimal losses. There are other ways to minimise the loss ratio too.
Also, 12 Constructors does NOT cost 5000 BCs. With a single engine, each construct costs about 225 bcs for something that can move at 5-6 bcs/turn. I don't build constructors that cost 400 bcs each. 12 constructs cost about 2500 bcs, or half the cost of your estimate. The ten turn estimate to arrive at location is based on constructs that use one engine.
You didn't say anything about engines, so I assumed you'd want to reach your target as quickly as possible. That would require at least two engines. Also, your cost seems a little strange. Assuming one Construction Module and one Warp Drive Mk. V, you'd have no Life Support Modules onboard. Otherwise, the cost would be higher. If you are using the Mk. IV drive instead, the base speed would be lower (4 pcs), but you'd have enough leeway in your cost to add several Life Support Modules. If it is the former, then your range will be pretty small. Unless you're playing on small maps, you need to build starbases to reach your enemy.
Also, nice double standard. Your Constructor design fits perfectly on a size 60 Cargo Hull, but for my Troop Transport, you expect Miniaturization research first.
Oh, and your 12 Constructors cost 2700bc, not 2500. It is also very different to what you said earlier (12-18 Constructors costing 2000-3000bc). That implied a cost of roughly 167bc per Constructor, not 225.
You're also forgetting that if you go with bare bones, you don't have access to advanced troop modules, and you're lacking in soldering, which greatly increases the chance you need more than 1 transport to capture 1 colony.
I already use more than one Transport per colony, so I'm not seeing your point there. My favourite race, the Yor, also start out with a big bonus to Soldiering, so the lack of more advanced Invasion techs doesn't hurt as much.
What you're not taking into consideration is military losses due to failed invasions.
You only loose Transports for failing an invasion, so I'm not quite sure what you mean.
Furthermore, your research numbers are off.
How are they off? I was using the Terran tech tree (like in the rest of my post), and have taken the numbers straight out of the game files. On Normal research rates, the numbers are only slightly lower than what I stated, but that also depends on map size.
Using the Iconian tech tree:
At the slowest tech speed, it takes about 17000 bcs to get all of the Cultural techs.
So, instead of using the Torians for your rebuttal, you use the Iconians, the worst race at military conquest (because they are missing some of the Invasion techs). Plus, you use Very Slow research rates for some reason. But okay. Let's take a look at your numbers. For the record, I'm using the values for a medium sized map. If you used a bigger or smaller map, then please say so.
Xeno Persuasion 1040
Cultural Domination 2083
Historical Assimilation 2083
Xeno Cultural Trends 3123
Cultural Insurrection 4166
Cultural Conquest 6250Total: 18745
In contrast, the military techs take:
6000 for Advanced Hulls and Medium Scale Building
Interstellar Construction 206
Expert Engineering 623
Advanced Hulls 1666
Medium Scale Building 2083Total: 4578
3000 for Space Militarization and Weapons
Interstellar Warfare 206
Space Militarization 419
Space Weapons: 315
Beam Weapon Theory: 102
or MD/Missile Weapon Theory: 632Total: 1042
(Beam) or 1572
I'm not certain how far up the tech tree this is supposed to go. Considering that the next point is basic weapon techs, however, I guess this is far enough.
5000-6000 for even the basic weapon techs.
Kinetic Streams I 632
Kinetic Streams II 1265
Kinetic Streams III 2532Total: 4429
Scatter Blaster I 315
Scatter Blaster II 419
Scatter Blaster III 1053Total: 1787
Seeker I 315
Seeker II 632
Seeker III 1686Total: 2633
13000 for Planetary Invasion.
Planetary Invasion 2532
Orbital Bombarbment 1686
Stellar Marines 1686Total: 5904
I guess you counted all of the Invasion techs. However, like I said above, the Iconians don't have access to some of them.
Or 27000 for a BARE BONES invasion and military force. And we're ignoring things like life support.
Still lower than the cost for the Culture techs (18745).
Also, your weapons will quickly become obsolete,
To say that weapons become quickly obsolete is quite a statement, considering that this depends on several factors, like research rate, map size (influences cost and possible research power), weapon type (influences cost), difficulty (bonuses for the AI, if higher than Tough), and the size of the AI's empire (research and econ power). It may sometimes take weeks, but it can also take months, if not years, for your weapons to become outdated. I've seen all of that happening since I began to play.
and more advanced weapons tech are exponentially more expensive than the previous level.
Some weapon tiers have a not quite linear cost increase, some have a static cost, but none have an exponential cost increase. The only thing, that makes Weapons research harder, is the Tech Inflation. Every time you research something (or buy/steal a tech from someone else), the cost for all your techs increases. Weapon techs, however, are hit the hardest by this increase.
Difficulty is masochistic/obscene. And no, I have not forced AI to max CPU. Does that make a difference?
It does. The increased speed, at which the AI is replacing designs, is only part of it. During your turn, the AI is calculating it's own moves. With more processing power, it can do this much better.
Still, if the game is as easy for you, as you make it sound, then turn up the difficulty to Suicidal. I'm curios, if you still manage to win with your strategy.
Finally, you only need a handful of starbases at a time because you're making progress continuously. Once you flip a set of planets, the next group of constructors will arrive to build the starbases to flip the next set of planets. At which point you disband your old starbases. The newly flipped planets will add their IP to the next group of planets, leading to a chain effect.
Still, placing influencer starbases in all of the enemy star systems at the same time would greatly speed up the process. However, you could only do this with small empires. Otherwise, the cost to place those starbases would get prohibitive.
The bribery costs are minimal since people you want to bribe the most (Korath and Drengin) are the ones least likely to get advanced econ/morale techs and are the easiest to bribe. They also have the lowest diplomacy modifiers.
Even if the costs are minimal, they should still be counted for your strategy, because they are a necessity. As for the lowest diplomacy modifiers, that's is only the case for the Drengin (and Thalan).
Sure they get more powerful, but I've noticed they're NEVER the most powerful in the game, tech or colony-wise.
It's a known AI issue of the Drengin, Korath, and Yor. They don't colonise planets within range of foreign influence. This makes them often loose the colony rush. There are some map settings that alleviate the problem somewhat. Abundant All and Tight Clusters are the best settings for them. Some others work too, as long as you make sure, that they start with a good amount of planets close to their homeworlds. Never use Scattered Star Density! That just cripples them.
I've noticed in my games the Altarians are always really pitiful, which means that it's easy to start a giant inter-galactic war by bribing the Drengin, Thalans (who also have major research issues early-mid-game), and Korath to attack the Altarians. It sucks everyone in, at which point you can ignore military.
Another known issue. The Category for Space Weapons is set to Point Defense in the Altarian tech tree. They will only research it, if somebody is using Missile weapons. In other words, it's unlikely for the Altarians to field a military. There are more bugs like this in the tech trees and other files. MarvinKosh, Tolmekian, MabusAltarn, and I, have released mods to fix those bugs. However, it's your own choice, if you want to use them or not.
All in all, I have nothing against cultural conquest. I even use it myself, sometimes, to supplement my military conquest. What rubs me the wrong way, however, is how you portray your strategy as the ultimate strategy. Even though, by your own admission, you haven't even tried it with the other races.