You used to be able to buy bags of coins from the US Mint at cost using a credit card. Some clever folk would continuously buy coins on their credit card then

You used to be able to buy bags of coins from the US Mint at cost using a credit card. Some clever folk would continuously buy coins on their credit card then turn around and deposit them in their bank to immediately pay off the credit card bill. They did this to rack up airline miles or something like that. That is why you can't buy money at cost with a credit card.