Making Big Money???

It can probably be done fairly easily on a huge abundant map. I've been close to 20,000 a turn on a gigantic but with occational / uncommon settings for planets. (don't remember exactly) Basically I just had 1-2 farms and 3+ stock markets on every planet, max trade routes, tax at 80%, etc. Nothing special, just a lot of it. That game I had most of my planets setup for just economics. I only had starports and decent production on a very small number of planets. One planet produced my entire military and it was building constructors half the time since I upgrade my ships instead of produce more. I just tend to favor economy > research > production. If you aren't able to keep your production / productivity at 100%, those factories and research facilities are just there going to waste. I also like that with spare BC you are incredibly flexible, buying galactic wonders the turn you earn the technology on a pitiful (but protected) quality 3 planet is nice so that you don't use up space on your capital planets etc. I also like how you can buy industrial sectors for every new planet you aquire until they are up to production whether you took it by force or culture flipped it, it makes them useful faster. It can be detrimental if you focus too much on money, and of course, as always, it's a matter of play style and preference.

Lots of people, high taxes, lots of stock markets, an loaded up economy resource or three, lots of economic starbases.

I don't overly load up stuff, but I have not had a problem getting to 3000 or 4000 per turn. I have never seen 20,000 per turn though.

lol yeah, i can do maybe 2-3k....i guess with tons of trading on well planned routes, some lucky Economy Resource bonuses, i guess i could see it happening......

Extreme Stadiums, Stock Markets and a cluster of huge pleasure planets.

Kinda strange though... my frontline planets are desolate deserts, with a few million working in factories like slaves, withstanding space battles, orbital bombardments... and my Approval is 99%!
What I found most strange is that though taxes are 80% people love me... now I think no matter how much tv channels you have, taking away 4/5 of your income is a bit much for any government

... huge pleasure planets.

I don't know about the rest of you, but I'd pay far more than 80% tax to live on one of these.
Of course I probably would stop working all together and not have to pay any tax that way...
Do these planets have good welfare programs?

Yeah, I had moral problems before but now I am at 80% tax and 99-100% approval and actually had a 100% vote in the star federation. I am getting about 2,500 bc a turn now. I don't like playing on maps with abundant stars as it kinda makes expansion not as crucial. I like having occasional settings so there are plenty of planets to build on but you need to expand to grow your boarders since some are further away from others.

It goes without saying you want Star Federation and other government techs too. When i hit the first government tech, my money woes are usually over.... And when i read the highest level with 75% economy/research/production, dough comes in like crazy