[loufe]

I can't stand forced product refills from the OEM. I refilled my Sodastream maybe a half dozen times before buying a 5lb tank, an adapter hose off Ebay. It paid for itself in 2 refills of the 5lb tank at a nearby homebrew store.

[SoftTalker]

It's a very old business model. Often cited in introductory businesss classes as the "Kodak model" (give away the camera, sell the film) or the "Gillette model" (give away the handle, sell the blades).

Generically you use the initial equipment purchase as a loss leader and then profit by marking up the required supplies.