In the past, it wasn't profitable; a $5,000 transaction required a transaction fee of ~ $40. Currently, it's slightly more profitable since the fee is ~ $20 ( $4,979). Reducing the number of slots might encourage more participants.
Yes, that's a good suggestion I believe because such a contest/raffle needs with limited slots will catch attention of the ones who always use the platform. Let's say if the total slots are reduced to 30 then someone with a single good transaction can fill all of those spots, then such contest will be like first come first serve basis for everyone. Those who join it early will win the raffle and take the reward.