A quote from Jason Brennan’s latest book, Libertarianism: What Everyone Needs to Know:
If Wal-Mart started to pay high wages, Wal-Mart jobs would become attractive to skilled workers. People who currently work as medical assistants or car mechanics would want Wal-Mart jobs. Since they are more productive and have more skills – since their labor is worth more – they will outcompete the kind of people who currently work at Wal-Mart. So, raising wages above market levels is unlikely to help unskilled workers. Instead, it causes job gentrification. (Imagine if Wal-Mart offered to pay its workers $100/hr. Then many of my colleagues would consider becoming Wal-Mart cashiers).