I think acceptable fees are 0.001 btc , 0.0005 btc then 0.0002 btc and below like for me this is affordable so this are fair for us users
Still i think better if the fee is only low like every transaction of btc because when we deposit in their gambling site because we already pay for that then actually i don't like to pay every withdrawal like i want one fee only for 3 times withdrawal
There should be no fixed withdrawal fee,and the only fee should have to be collected it miner fee which sounds good because gambling sites already making through bets then why they are making few bucks via withdrawal process which is really not necessary.