How does a shop normally deal with such errors?

I went to builders ware house in Hendrik Potgieter in Roodepoort to buy doors. The prices were displayed directly on top of the doors. Upon requesting for 5 doors I was told no the prices were incorrect and that the people that worked the had mistakably put on the wrong price tag. I was then told that I would have to pay using the correct price . This was very puzzling and I had informed them that I had hired a bakkie and had incurred costs even cause of their mistake but the manager just did not give a damn.