On another more on-topic note, what an awesome time to be alive! :) When I was younger concepts like this were usually paired with flying cars and space travel in cartoons, but now it's real.
No, you're wrong. If it can be done it will be done. It's just too much reward versus the risk. Stealing this way scales too well. In a normal shop the risk of detection is variable, and therefore higher on average. Sometimes people will be alert, sometimes not, sometimes there will be guards sometimes not. Now this is different, it's all down to following the correct number of steps to get the desired results.
If you replace these two stickers, now scan this then switch this...
It'll be down to a few bits in some chip somewhere that decides how much you need to be billed. I'm sure it won't hurt adoption or even lead to a significant increase in lost merchandise, but I'm equally sure it will happen.
As for plain old physical theft:
Oh here is an interesting exploit. Buy or steal a $20 "VISA gift card" register an account with that as the payment option, walk into the store, grab $500 worth of steaks/liquor, walk out.
I worked at a food store as a starving student and we had interesting problems with people loading up carts and shoving them out the fire safety doors into a waiting pickup truck and driving off. If you allow people with false ID into the building, you will get ripped off. I can assure you police are completely uninterested in video footage of shoplifters, probably due to the near infinite volume. If you can physically get away, unless you achieve felony levels of theft value, you're simply free. This might have interesting long term implications for whats for sale as fewer and fewer people have higher and higher paying jobs and everyone else is perma-poor, such as this tech might scale for 80 pound bags of rice and flour even when almost everyone is poor, but not jars of caviar and $300 bottles of liquor and rare wines and jewelry stores. Salt and pepper, sure, saffron threads probably not.