Not every casino will charge a high fee. Depending on the amount and also depending on the payment method. There is still a lot of difference.
A small fee is manageable, but if the amounts are high it can become expensive. At the end it is the call from the casino.
It would become expensive when the entire network is clogged which is a common scenario everytime the market is really that on high traffic where people
do trying to pile up or setting up those high fees for their transactions to be prioritize and of course miners will be choosing it first.