Very possibly.
A receipt for payment is surely evidence of sale, and as I said above, in a shop the item and receipt are simultaneous - thus, if a mistake has been made it's then too late for the seller to retract.
Over the internet, that is not the case, and it would appear that the receipt has no legal consequence, as the seller has more time to realise his error, and renege on the sale.
In a shop, of course, the possibility of carrying through the error to point of sale is more likely, because the original pricer is unlikely to be the individual on the till.