The bank event usually draws close to 500 because a paid enry entitles the player to a door pass for the entire event. I am not sure if they cap the entries at a certain number since this is not a traditional double elim bracket tournament. The draw is done prior to each round on a single elim basis. An eliminated player does have an option to rebuy once back into the tournament.
I can't remember the player totals from last year but I think there were over 200 in the onepocket and nearly 400 in the 9 ball.
I think I read somewhere that the limit is 500 this year. Personally I think it should be lowered a little, maybe 300-350 The main room is so crowded sometimes you're shoulder to shoulder with people pushing against you from all directions.