[r00fus]

Do these kind of arbitration opportunities still exist except as mistakes? I assume that channel would have been made unprofitable after discovery...

[fennecfoxen]

It's arbitrage, not arbitration. I believe the mint began by denying orders from people suspected of being crazy-exploitative, and ultimately terminated the program altogether. (You can still order the coins, but you'll have to pay for shipping.)

[dkfmn]

Almost every credit card changed their terms so that cash equivalent purchases no longer accrued perks.