I don't think it's a lot to ask that I'm informed how much I'm going to be charged before I pay for something, which is the process for every sale I make currently works.

What if the item is marked as on sale but the database hasn't been updated so I don't get the sale price?

What if the price on the item is correct but someone fat fingered the price in the database?

What if a different customer moved an item from one shelf to another so the price on the shelf is for a different product?

What if I want to know the total with tax?

What if a camera sees me pick up a $500 item to look at but doesn't see me put it back on the shelf?

I don't want to go home, wait an hour+, see I've been mischarged, and then have to spend a week waiting for a refund to process.