How has nobody mentioned the worry that you'll get overcharged? I'm sure computer vision isn't perfect, however close it may be, and once you've left the store (presumably when you'd check your receipt) there's no way to prove you didn't take whatever you were charged for. I'd be pretty worried about accidentally "buying" something I didn't actually take, even if that's statistically unlikely. (Yeah, I know, it doesn't make sense to worry about a 1 in 10,000 event, but people aren't rational.)
Or, if they decide to side with the consumer and give you your money back, then that opens them up to theft - go in, buy stuff, "oh I didn't buy $expensive_item!", get money.
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