For the Yor, it's not that bad once you reach Enhanced Collectives. While 3bc maintenance for 9mp production isn't great, it is much better compared to the 5bc for 8mp of the Xeno Factory. The buildcost of 150 is also reasonable. Just a little more than double the original cost. Considering that this is the second improvement to the basic Collective it is still okay. Once you research Superior Collectives, however, things change dramatically. Both buildcost and maintenance double in size for just 2mp more. How is that "superior"? Granted, it is comparable to the Manufacturing Center (6bc for 10mp, buildcost 150), but who would use it? Staying at the Enhanced Collective is much better, not to mention more efficient. For a race that is all about efficiency that is pretty bad. The Ultimate Collective doesn't make it better either. For the last two mp, the buildcost increases by another 200 (roughly 166%) and you have to pay 2bc more maintenance. Again, it is still better than the Industrial Sector (10bc for 10mp), but that isn't the point. Why does going from 5mp to 9mp increase the buildcost by 80 and the maintenance by 2bc, while going from 9mp to 13mp increases them by 350 and 5bc respectively? It just makes no sense.
The Torians have it even worse. Going from Schools to University increase the buildcost from 25 to 100 and the maintenance from 1bc to 4bc, while the research only increases by 4rp. Going to City of Learning then triples the buildcost (100 -> 300) and doubles the maintenance (4bc -> 8bc) for only 2rp more output. How does that make any sense? Granted, the Torians are supposed to be bad at research, but this is just rubbing it in. Also, who in his/her right mind would use them? You're better off building three Schools instead. The buildcost is less than a third and the maintenance is not even half of that of the City of Learning, while producing 2rp more. Sure, it will take up more space, but that shouldn't be a problem, because you have more time and money to spend on expanding your empire.
Yes it's true, the progression from enhanced to superior collectives is a big step, and it's something you don't want to do always. It depends on a lot of factors, and this will also differ from game to game. For example if you are amidst a war and your MMR is kinda dropping then no, don't do it, production of ships is more important.
But let's say you've just conquered someone, your planets population should regrow again, there's no wars going on or hostile empires nearby - then why produce military ships that cost alot of maint for no real purpose? Maybe producing constructors and filling up your space with starbases - but that will come to an end, too, esp. that SB become excessively expensive to built once you got around 20 or 30.
So just upgrading your coreworld to the next tier while the new planets desperately need the SP to fill their tiles. (although one could go all-lab and build everything with focus from research or buy all structures but that's a whole different story... in my games I just reach that point where my planets are in a complete different state of evolution and thus, I always enjoy having something in the queue)
Another thing is that you're comparing only the base output of these buildings.I think it's safe to assume the farer a game advances the more empire-wide bonuses you'll got on these through Crystals, Starbases, Techs, other buildings etc. Sometimes base production will bring twice or trice the output - and you just pay half for that.
As well as in later stages of the game, where the economy is going good, I don't think that the maintance of planetary buildings is actually a big factor.
Then there are also bonus tiles, these are very suitable for highend buildings. Or maybe you got a few specialized planets with ManuCap or similar percentagebased production-enhancing buildings - most of them are also only viable on special planets, on most not.
Maybe a planet where a special event happened during colonization giving increased ships HP - further add the Orbital Command Center, and this is your planet where you're going to build extra-strong and longliving warships. You want to have as much as MP as you can on that planet, irrelevant of the costs.
To be honest, I think there should be even more traps esp. later in the game (although it would require that the AI is aware of them). Because most of the time, once you've conquered or anexed the first or maybe 2 empires, the game is usually won. The problem is that by that time, once you gained an edge over the others this edge will grow stronger and stronger, and that growth will be faster than that of your enemies.
Once you're having more production, and you're using that to gain even more production, if there is not some overlying mechanism involved which is stiffling that (like increased cost/maint) then the whole apparat would kinda explode once it is set in motion.
Although there actually is something governing over that, and that is the economy, you gotta pay your stuff. And the economy is actually something that will be very low in the first year, and probably even preventing you from keeping the slider at 100% all the time. But between y1-y2 usually, if the game is going well, you should have a steady and fair income and that's giving you even the option to buy some stuff every turn.
What does happen when this is not in place? I just could see that with stockmarkets in the DL game. I would colonize a planet with 1000 colonists, and immediately lease-buy a stockmarket on the longest-term lease. At that population that investment would already net more bcs per turn than I would have to pay (23bcs vs 19bcs if my memory is correct) and that would even increase each turn as the population is even growing stronger cause without economic problems you can lower taxes to gain 100% approval! I then lease-bought as much as stockmarkets as were affordable and after 5 turns could leasebuy a stock on all planets, and subsequently after 4-5 turns could leasebuy one hull on all planets additionally - the economy shooting from 15k/turn to over 100k/turn.
And this is bad design in my eyes, one should not be able to exponentially grow an advantage over the other, rinse and repeat, and game is won. Nobody can keep up with that. Once you've reached that threshold it's game over, and it's boring from that point on.
You can see it in the respective curves - these were exploding. Curves should rise linearily *at best* problably even less. So even that lesser strong empires should be able to keep up, this would in fact promote longer games. But the question in charge is - how would you do that?
Because, everything that you're usually doing is giving you an advantage and that'll invested each turn to gain even more advantage. Although advantage is probably an inappropriate term for that as it is relative to what the others are doing. However, you will gain a return for whta you're doing each turn, and if you're doing it right, that will become bigger and bigger and bigger, and the only thing that could cross that pattern is an enemy empire growing nearby.