Here's the highest paid bowler I could find from last year:
He made just over $300k. This year he's made $31k so far. He's 45. I bet these guys could get more money for NFLers when they retire from football. Bowling is an old man's game. Athletes probably get higher appearance fees for an event than these Bowlers make in a year.
If they really got a celeb league going, they could probably get all the PBA guys to join them for the ability to make more money and get more publicity.