This helps, but it still doesn't explain what Market Centers do. How do they help my income rise if nothing new is being created?
Actually, the Economy article listed above has a hotlink to the
Wiki tax article that gives a more precise and useful definition of what your planetary income will be. Basically the short answer is more people equals more income. Also the various bonuses make a huge difference.
You mentioned another key item in the OP which is that morale and income are intimately tied together. Anything you can do to improve your overall morale will allow you to use a higher tax rate and therefore have a better income.
Certainly the obvious things about getting a good ecomony are things like economic racial bonuses, political parties that give an economic bonus, economic resource mining and various technologies and wonders that give an economic bonus. One of the biggest is the Mind Control Center which gives a 100% economic bonus but can only be built by evil civs.
Just as useful are all the similar abilities, mining, tech and wonders that give morale bonuses. Finally, one of the most neglected are the pop growth bonuses. These can be very powerful in being able to quickly develop planets to the point of profitability since more people quicker equals more money sooner. Also colonizing planets with as high a pop as possible assures that they grow as fast as possible and thus becomes profitable sooner. It can even help to use colony ships to "bus" more pop to newly founded colonies to speed up their development.
As far as the idea that information is hidden intentionally for the benefit of those "in the know", I really doubt it. The tax formula's were decoded mainy by Iztok with some help from others if I recall, and do provide total information into how the ecomony works, however I really have never found it a requirement to know any such formula precisely, it's merely sufficient to know that the more people you have the more income you make. And that the more economic buildings you have the more income you get from the people you do have. That's really all you need to know.
The hard part is as you alluded to, the fact that there are so many ways to proceed in this game and that everything is a balancing act between a mad rush to gain planets early and being able to develop the planets you do have. I've found that I've often done better in games where I've intentionally slowed down my colonization rate just so that the planets I do have end up stronger quicker. I call this the quality not quantity method. Again it's a balance because if all the AI's out colonize you 2 to 1 and you give them space to develop these planets then you will have no real chance. If you go this route you need to be ready to attack them before they have much of a fleet and the bulk of their planets are weak and easy to take. I look on this as merely the 2nd phase of my colony rush. This has the benefit of taking over planets where someone else has already built that first factory for you. This gives you a big leg up in development. It's great when you can get the AI to do some of your work for you.
Anyway, these are merely a few ideas out of the myriad possibilites of ways to play this game.