You might want to look into a personal shoplifter.
HILARIOUS! Well played!
Then some store, to save money, had the shoppers come in and shop for themselves - so he made the grocery cart. It didn't go over well at first.
I would go back to that system. Have the groceries sitting in individual cages and coolers that can be watched by one guard and can be opened with a credit card, or have one or two attendants that can take cash.
The prices probably wouldn't change much due to fewer to no product loss. And if the shoppers complain, tell them “Well, it was either this or we were going to close down and move 50 miles away.”