That's because while the clothes themselves are sold for 10x or 100x the price they cost to make (which is dirt cheap, these stores pay the sweatshops close to

That's because while the clothes themselves are sold for 10x or 100x the price they cost to make (which is dirt cheap, these stores pay the sweatshops close to nothing), the difference is spent on having stores in high rent areas in most cities. This is part of the branding strategy for stores like H&M or Zara. Many of the items on sale are of similar (or slightly better) quality with what you find in cheap outlets at the edge of the city, even the ones that sell en-gross. But having a store in an affluent part of town gives them more credibility and a better image.