It is a store, a business, and a well greased one.
Pays (european) salaries, (european) rent and (european) taxes. They have a repair shop like nobody else in Europe, and probably in the world, to verify and repair (when makes sense economically) photographic equipment. On top of that, you can return an item before 30 days without question asked, and have a 6 month guarantee for checked items or 12 months for repaired ones. Comparing them and their prices with eBay or craigslists-like sites is absurd. Their continuos grow since they started indicates that they were right and others wrong.
My whole experience with them is buying a filter and selling my complete and beloved Mamiya RZ67 equipment. Perfect service and excellent communication.