It's not a lot at all. It's an easy to build tower pared down to Shuttle proportions, made from easier to source and update components, without the size and weight of a monitor to increase storage/shipping and build costs, that can EASILY be built to varying specs. It has appeal to the 1000's of school boards with perfectly reusable CRT's, business who just want a bare machine, consumers who want a bare machine, consumers who want a LOADED (but small and relatively affordable) machine, and it can all be built on one assembly line using whatever parts are cheap and plentiful during the regular update cycle.
Translation, increased sales and profits WITH lower prices. YAY!