> The only problem was most cashiers actually knew all the prices of stuff and paid attention,

Yup. I was in a local super market and saw Tomahawk steaks priced at $4-6 each. It had to be a mistake but I figured I would give it shot and see if they noticed. Cashier looked at the price, did a confused double take and immediately called over the manager. Turns out the decimal point was off by one so my $4.50 tomahawk was really $45. I bought it anyway and it came out great in the oven.