When I went to buy The Witcher 3 GOTY Edition which was on sale at Christmas, it said £19.00 on the shelf, yet at the checkout it scanned at £9.00... I said nothing.
This is also the same store where me and my girlfriend bought our Switches, should have been £280, but they had an offer on, get £20 off electronics when you spend so much, and the Switch on its own qualified for the offer, which instantly knocked it down to £260... but then again at the checkout, it scanned at £160. I wasn't planning on buying one that day, just tagged along with my girlfriend to go buy hers, but when I saw it was almost half price, I bought myself one too lol.
They seem to have a lot of problems when it comes to pricing it seems, lol