Wow. One one hand, I'm glad that there are so many honost people out there.
On the other hand, I consider myself a very kind, caring, honost person, and I would not go back to the store. I drive 30 minutes to do my grocery shopping. I have bought things, and left them at the store accidently. I have never once gone back for them. I don't imagine I would go back if something wasn't rung up properly.
It's definately something to ponder.
Although, I do watch the register pretty carefully, and on MANY occations, double check to make sure they got everything, if I don't see them ring it up.
I'm the same as you. I try real hard to pay for everything and would never think of stealing. But, on the one or two occasions that I've gotten into the car or home before realizing I was undercharged for an item, I didn't go back and tell the store.
Honestly, I figure that the rare instance where I have not been charged for a low-ticket item probably evens out with the times that I get overcharged for items.
Once or twice I have noticed an error in the favor of a store while still at the store and do get it corrected then.
One note, the few times I've had this problem, it's always been an item that was towards the back of the shopping cart or that I'd handed to DD and I couldn't easily spot it because it was underneath the cart's child seat (with DD sitting in the seat, thus blocking my view) or DD had dropped it into her seat cover. I try, now, to not let DD hold any purchases and to doublecheck to make sure the cart is empty when I'm in the check-out line.
For a high-ticket item, like several cases of beer, I would pay for the item the next time I was at the store. So, I guess I have a price threshold.
In a similar, but slightly different, vein: A few months ago, I was shopping for a windbreaker-style jacket. As it was springtime, these jackets were in-season and I priced out several nice ones at ~$80. After much ruminating, I finally decided I was grudgingly willing to part with that much money for a windbreaker. When I took the windbreaker to the cashier, it rang up at $35. I was quite certain the jacket was NOT on sale (no sale sign on the rack, no coupon, in-season item, etc...) and the price tag definitely listed the price as ~$80.
Would you have alerted the cashier to the discrepancy? Would it have mattered if the cashier was surly? How 'bout if the cashier was in the same area as the jacket (woman's dept.)?