I reckon the shopkeeper thought he was 'getting one over' on some old duffer who (being over 50) would obviously be clueless about newfangled crackle-magic devices. There's nothing like letting people think that *they* are robbing *you*, to pull the wool over their eyes.
Saw exactly that dynamic in a story a few weeks back about a US pawn dealer getting burned -
"On Feb. 3, a downtown Port Angeles business, EZ Pawn, paid a person about $20 each for more than 20 counterfeit U.S. Morgan silver dollars that were supposedly from a century ago...
Brian Winters of EZ Pawn has bought coins for years — and even he was fooled. Unlike most counterfeits, the coins did not all have the same dates. One was a super rare 1893S, worth thousands and thousands."