I also accept a dynamic fee based on mempool state, or a priority approach (pay more if you are in a hurry)
What I do not consider fair is when only a huge fixed fee is proposed, like 0.001 BTC. That really discourage crypto gambling in my opinion.
For me, the withdrawal fee that I consider fair about to 0.0002 BTC below, but depends on the traffic and adjustment of the sites. Now new gambling sites are adjustable on their payout system because of the traffic on the blockchain. But it thinks 0.001 BTC of a VIP withdrawal fee will be fair, like in the regular casino if you are high roller your costs and exchange is different than others or like choosing your transaction payout speed that will depend on the level of fee.