Unfortunately no details were given about what makes 50% of all bitcoin transactions “fraudulent” ? What does that even mean? * did someone try to send something other then bitcoin to a ₿ address? * did a client claim he payed and did the payment seem to fail on his end? * did a client not realise that you as payee also pay for the network fee? Nowadays these kind of problems would be easily prevented by using bitcoi…
If Valve didn't want to see any forex risk on the sale, they end up incurring it on refund. If people are using it as an easy way to store money in USD and then convert back to BTC when the rate goes up, that can get expensive in a hurry.
It could also be that they used Coinbase or some other provider to act as a processor, and Coinbase charged the merchant if there were chargebacks on Coinbase's accounts.