Zeusmix does not charge a fee for refunds. Refunds for TRC-20, BEP-20, and ERC-20 tokens are made by sending the user the private key that holds their funds.
Anyway, this is the weirdest way, potentially causing further problems since private keys are not supposed to be shared between 2 or more parties. If I somehow get caught on AML radar, I can just withdraw my funds while I file complaint that it wasn't me who did it.
When I know my private key and I shared my private key with you then it's me and you. According to Zeusmix terms, they will share the private key to the customer who is expecting the refund. Which means Zeusmix and the customer only know the private key.
The same private key sharing model business was done by a highly established crypto service not long ago. They were doing the business successfully for around half a decade. I do not think this is going to be a problem at all.I remember that highly established crypto service. But I also remember that they share private keys in form of "Chips" and they promise that it should be automatically deleted after 7days from their servers. This means that the custmer will be the only owner of that private key if he would prefer not to withdraw it to his own address. Then what happened? The service was seized, and several terabytes of data were seized from its servers. Among that data were private keys for chips that were supposed to have been sent to their owners more than a week ago, which means that they have not been erased. In fact, this was confirmed through complaints from users, some of whom confirmed that they had been keeping those private keys for more than three months.
I still think that this cannot be the best way to make a refund for the service that is the subject of our discussion now. Especially since there are other ways that are smoother and safer. I mean, I don't see a need to devise such methods that may not be accessible to everyone. I'm sure not everyone is good at handling their private keys carefully.