>It seems like every financially successful developer out there came from a middle/upper class enviornment.

I think this is more likely evidence of how many advantages being brought up in those environments gives in becoming financially successful. Not having to worry about paying for college, for example, leading to having more seed funding to be able to start working on your own projects, and potentially even having relatives provide that funding directly.

Even then, only the greedy find major success. Make the cost of living lower, and you see more successful people, specifically more guys like Thibault who are willing to do thinks the right way.