If you buy a fridge at home and pay say 1,000 US$ for it because the salesman told you: cheap offer, you could be happy with it. If the next day you find out the standard retail price is 800 US$, you could go back to the shop and try to get a refund.

But: you were quoted a price and agreed to the price, there is no obligation from the store to give you a refund.

Same situation here.