Starcraft is basically a sport like baseball, or soccer in Korea. Players get sponsored by big corporations like Samsung. In the OSL, first place prize is about $40,000 USD with second place being half. And since most players are around 20 years old, that's quite a fair bit of cash. It was from a commentary, but considering that pro gamers are basically celebrities in Korea, it's not surprising. The games are broadcast on TV, the players get interviewed, and probably end up on magazine covers and such. I mean, take a look at Brad Pitt. He's considered one of the most attractive men in the world, and many women would love to see him live. It's the same thing, fans want to see their favorite players so they go to tournaments to watch.