It is very smart of Walmart to use 5 L SOPUS jugs for regular prices and 4.73 L SOPUS jugs for sale prices. Forget the price matching thing, because their 4.73 L rollback stuff is always better than whatever their competitors sell (i.e. CT usually with the 5 L, sometimes the 4.73 L).
They don't have to ever adjust the prices for the 5 L jugs, except for occasional price increases (and non-existent decreases). When they want to have a sale, put out the 4.73 L jugs and the price is set. When the 4.73 L jugs are out of stock (sales always seem to be while quantities last), then the guy who missed the last 4.73 L jug and bought the 5 L jug pays the big bucks. When the 4.73 L is gone, it's done, and they don't have to do a thing with their till pricing.
And, as you say, if the product is still in stock after the sale is over, the sale price is still honoured. So, the customer who is lucky or pays attention gets a good deal.
