<p>Simple arbitrage… Good idea.</p>
<p>A while ago the US Mint (?) was offering free shipping on purchases of 1000 US Dollar Coins. Of 'course no one wants them, so people would buy them with cash back credit cards (I think they go up to 5%) and then just take the coins to the bank and deposit them. Free $50 everytime, minus the gas and time cost of getting them to the bank. This no longer exists by the way.</p>