I don't have account in that platform because their services are not available to people from country, something I find very strange, I know the fee is high. If they can add Litecoin and Withdraw via USDT Bep20, then those will go with very low fees. Most of the popular casinos already have these options to make it easier for their customers because $2 is such a big money that can earn you several spins in slot game.
I was talking about the network requirements of Tron. That's what you need to pay if you send USDT from a non-custodial wallet. Centralized services, like casinos or exchanges, are free to set their own requirements. They can charge players absolutely nothing or ask them to pay whatever they believe is suitable. As has been reported in this thread, bet105 has decided to cover all network fees for its players from its own pocket.