It can take such "fee" because it’s so enormous that it can negociate prices in a way you couldn’t, as well as handling the logistics and having lots of different products at the same place. It’s not "just an intermediary", it’s an intermediary that adds value.

If you want to eat a yogurt, would you prefer paying $4 a pack of four at Costco or $1500 for 4000 yogurts you have to transport from the manufacturer to your home with your own truck?

Disagree.

A retailer does add tangible value beyond matchmaking.

For example, to name a few:

    - transport
    - quality control
    - inventory management
    - fine-grained understanding of local demand and providing the corresponding supply.