If you are in the top 23 players in the world, you will make a decent salary, comperable to a secratary at a decent company.
If you are in the top 50 players in the world, you will make just above the poverty line.
If you are anywhere below that, you will work at McDonalds.
AND NOTE: the best players play all day to practice. It is work for them.
EDIT: Compare that to anyone in the NFL. This is absolutely worthless as a money-maker. Maybe if you are in Korea and 10 bucks a month will sustain you.
But any sport is a terrible career if you aren't the best. There's probably a million of guys in internet cafes wasting their time and money trying to get that good.
I'd even argue that those people winning at SC2 are probably the same who were winning in SC1, and possibly other games, so they may wind up being the few lucky ones. It's like hackers, not everyone will be the next Zuckerburg, but the average pay is damn good, whereas with gamers, not everyone will be the best, but the average pay sucks.