$1500 prize is an enormous amount to reward the users periodically.
Certainly there will always be a lot of competition for a share of that prize. It also shows how profitable this casino is!
Most of the user that participating in the tournament do a calculated gambling therefore they weigh in already the potential profit and loss if they compete on this kind of tournament that push user to wager huge volume to win that prize.
Assuming that there will be a toe to toe battle on the top 3 spot, I think all of them will be spending more than the rewards allocated on the tournament just to protect their rewards that allocated already as their cashback.