For the most part they aren't getting paid to play, they just play for free. Different pro teams have different levels of compensation, some give the players nothing and others are paid.
A lot of players look for jobs within the industry, that way they have the flexibility to take time off for tournaments and practices while still earning a paycheck. To play at the upper levels takes more commitment than just practicing on the weekends, you add in physical training and even daily drilling for some of these guys and you see that it's quite hard to hold down a steady job.
While a big name paintball player really isn't a big deal to you personally, to a lot of people it is. It's the industry equivalent of buying baseball bats from Cal Ripken.