I know of a similar situation. The old castaway tackle in north van had a guy who was coming into the shop every X days and paying down a $400 or $500 center pin. This was a set up between the owner/operator of the shop and a friend. Anyhow, every time he would make a payment, the owner scratch a line thru the price and write down the new total. He needed to be away from the shop one day and he had a buddy watch the shop...wouldn't you know it, someone walks in and says how much is that center pin, the guy not knowing any better picks it up and see a price tag with several scratched out prices on it bringing it down to $225 so he eagerly snapped it up.
That caused quite a S**T storm as you can imagine, but the key is that the product made it out the front door due to the ignorance of the shop keeper's fill in. Ya sure I would stand at the til with that rod in my hand and made as much of of fuss as possible in order to get that rod but really I can't blame a private business man for not honoring a OBVIOUS mistake in his pricing.
Let me ask you this (and I have done it before), at the atm depositing a check, have you mistakenly put in the too little, lets say $1000 instead of $1100? Ghost Fish and RVT, do you think they should consider keeping the difference because of your mistake - ha ya right as if!
BTW, when I did just that, I got a notice from my bank telling me that my deposit was 17 cents more than what I punched in so they credited it back to my account.