Yeah, that "computer error" explanation is bullshit, probably rooted in a combination of CYA and narcissism.

When I worked in retail, we only had one database of pricing. The shelf tag and sign printers, the registers, the whatevers -- they all used that same database. If a shelf tag was printed at the same instant that an item was rung up, then they'd have had the same exact price.

There's mechanism for the prices to deviate.

(And yeah, pricing errors still happen at least because people are people. We make mistakes. We forget shit. We can even convince ourselves that we did a thing even if we didn't. We err. Even if we're absolutely honest with ourselves and others, we can run out of fucks to give. It's all part of our condition.

But of course: When a price was posted wrong then we fixed it once it was brought to our attention. The customer got the price that was posted, and the posting was changed.

For my own purposes, I had a habit of pulling the incorrect price tags and taking them with me back to the register; I'd just give them to whatever manager when they would show up with the key that was required for precise price adjustments and get back to doing whatever it is that my primary job was at the moment...which, if I were handling a register, meant something other than printing shelf tags.)