No, he might have standing. If there jurisdiction requires that incorrectly priced items be sold at the marked price then he will. If they are like most places where the seller cannot be held to sell at an incorrect price then he does not.
Since we don't know which is the case saying for sure the he has standing is misleading. The information we have now is, "but I want to more sir". Compelling items to be sold isn't a common thing. Sellers can choose to decline sales.
He would have a far better case if the situation was that the offer to sell was withdrawn after they found out it's intended use. That does not seem to be what happened here. It was a simple pricing mistake.
