A year or two ago I had a cashier ring up my zucchini as cucumbers because he apparently couldn't tell the difference. Young guy, looked barely 18. I have no idea if he overcharged or undercharged me as a result, but I didn't care enough to point it out because he seemed like the type who would have needed 20 minutes to figure out how to change it (or would have needed to call down a manager for help) and I didn't want to waste any more of my time (or his).

> The visual risk of walking out without paying is much greater than the risk that anyone actually investigates AND tries to track him down for it.

So scan everything, then put it in the cart and walk off without putting in the credit card. Again, both are stealing but paying some fake, reduced rate is leaving your calling card at the scene of a crime.

> 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.