I believe you can pick up a prepaid debit card (e.g., $5) at retail (e.g., convenience stores, drugstores, Walmart, etc) which can be loaded with Moneypak up to $500 USD (without registering it). So the total for fees then is about $10. For $500 that's about a 2% fee.
To avoid some confusion there are non-reloadable prepaid cards. These don't use moneypaks. You simply buy one for face value plus ~$5. $505 for $500 card. You can use it until funds run out and then throw it away.
There are also reloadable cards however you can't add a MP to a reloadable card until it is registered and registration requires KYC information (name, address, SSN, etc) and are only available for US residents. You load them with an initial load of $500 plus ~$5 card fee at the time of purchase. In this respect they operate the same as non-reloadable cards. However if one doesn't intend to register the card they provide no advantage over just using a non-reloadable (essentially they are non-reloadable until registered).
You can thank KYC, AML, Patriot act for all this nonsense.