That's fine for small sellers, but dealers that list thousands use listings tools and mistakes can and do happen sometimes. There's only so many hours in the day to preview every single one
I dont see how the ease to not make an error posting makes it okay to take advantage of someone when they do make an error posting. Its almost like you think they deserve what they get for making a mistake in their listing. Why? Why not just message them their error when it's clear?
I dont have an opinion on what they deserve. If they see the error after it gets purchased then they can just cancel the transaction. I have seen it done and have had it happen to me personally. Im not gonna argue about what happens if a seller puts down the wrong price. No one's minds will be changed here. I commend the op for their honesty. You dont see that very often.
If you walk into a retail store and see the right item with an erroneously-low price, do you insist that they charge you full price for that item? How do you know what the full price even is? Looked at from the other direction - since this is what I do for a living - if I label an item with the wrong price, I have to honor that labeled price. That mistake is on us, and we have to eat it.