This is rather normal on exchanges when depositing currencies on the wrong chain, ftx and Binance both have their fee if you want to recover funds that were deposited on the wrong chain.
OK, I think it'd be just good customer service to fix the problem without charging the customer for a silly error like this--but to charge $500? That's just a straight-up shitty practice, and that tells me they're willing to gouge anybody and everybody they can, because obviously they care more about $500 than they do about keeping someone using their exchange and/or about a disgruntled customer creating a black mark on their reputation like OP did.
I've never heard of BKEX, by the way. Are they a really small, unregulated exchange or one that just services a single country or something?
At this point im in serious doubt about if they will really transfer the tokens back after I pay the 500USD fee or its just another systemic scam of this exchange....
I'd be in doubt about that as well, and I bet you're quite conflicted as to what to do. That's a lot of money you stand to lose if you don't pay them, and if you do, you run the risk of them stealing another $500 from you. I wish I had some sage advice for you, but it's a tough call on this one. If they don't have an extensive history of scam accusations against them, I might send the $500 (even though it's outrageous) but again, I don't know anything about BKEX.