I don't know why the Mint would be upset. Arbitrageurs doing this will force banks to stock-up on dollar coins, which would presumably make banks more likely to

I don't know why the Mint would be upset. Arbitrageurs doing this will force banks to stock-up on dollar coins, which would presumably make banks more likely to circulate dollar coins to retailers. Thus, dollar coins will increase in circulation; the Mint should be happy about that.