$$ in game development

If it were just you who made, marketed and published a game that was as successful, commercially, as Halo 3? Then yes, you could.

However, that is effectively impossible.

Beyond that, your question is too broad. "It depends," is the only reasonable answer.

this is just brilliant!

>> I was wondering how much it's possible to earn on game development.

It is work. I'm glad you said "earn", because some people feel that just creating something and offering it on the web means they are entitled to money.

You may choose to develop games for other people, and earn a good salary.

You may choose to develop your own games, for no salary.

If you make your game, you must complete it on your own, with no outside money. Only after it is complete can you attempt to sell it. Any success at selling the software is highly variable based on a boundless number of variables.

This article in the reference section covers the main difference between an unprofitable and profitable game developer.