Yeah cos ASDA supervisors must be earning so much money that they can’t help but be eager to do everything possible to help a multi billion pound business recoup a £3 mistake. I know it shouldn’t be that way and in a lot of cases isn’t. But then again in a lot of cases it is.
A lot of shops, especially supermarkets will honour a pricing mistake as they value the feel good factor more than a few quid (though it might be different now that so many sell high value consumer durables. I wonder if they honour a mistake if a TV that should be £399 was accidentally labelled at £3.99.
My understanding is that no shop/retailer is obliged to sell you anything, just like a pub isn’t obliged to serve you. As said positive/negative feedback may/may not be important to them.