Outgoings are different - cheap/dodgy imports, and modern slavery (nail salons are infamous for this) mean that their outgoings can be much lower than other shops. There’s also the tax avoidance many of these businesses partake in, both in the traditional cash-in-hand-business fashion, and the more modern(?) “American Candy store” way (https://www.bbc.co.uk/news/uk-england-london-61777445)