Price difference on checkout

I added a jewellery item to my cart but on check out saw that the price changed but when I double checked the item on the product page, it definitely shows me a sale price. Queried this with Takealot on 08/09/17 and had to follow up myself on 11/09/17 only to be told the following:

"The cart updates in real time (on check out) and hence may differ from the original product page which may still show stock available at the deal price. This is because the product page takes longer than the cart to update."

Essentially making their problem mine after I had to wait on feedback AND lose other items in my cart to deals/promotions ending because they took so long. Why should a customer bear the brunt of the system not updating in real time?! As with any other retailer, I want to pay the price I see in-store. I'm not interested in delayed system updates or errors.