Same same but different
If you’re traveling to a hot tourism destination, never shop at souvenir stores unless you want to pay more for less. You can get souvenirs from road-side sellers for much less than at souvenir shops since they incur lower overhead expenses. But that’s beside the point. The OP offers another reason why you should avoid souvenir shops.
They worked at a particularly famous souvenir store in an unknown city and later learned that the other neighboring stores belonged to his store’s owner or family members. Each store offered different prices, some lower and some higher, but the money would go to the same family. “Don’t buy from Store A! Get your souvenirs at Store B, which I also own!”