Movable Glass Walls Inc. constructs folding glass walls that are engineered to accommodate the weight of large glass panels. The engineering allows extra panels to be added in a linear fashion (as many as the opening width requires) the outer frame being around 80mm can replace what is generally already there without re-designing your whole house.
Why the big difference in cost?
While French and Sliding Patio Doors are pretty much available off the shelf Movable Glass Walls are usually made to measure.
French and Sliding Patio Doors are manufactured to operate adequately using standard low cost hardware like hinges and rollers.
Movable Glass Walls on the other hand, usually require highly engineered precision hinges and rollers. Movable Glass Wall hardware needs to be technically superior to the hardware used in French and Sliding Patio Doors. Consider that Patio or French Door hardware will be expected to carry less than 180 kgs of glass in either a sliding or swinging motion.
Compare this to a Bi Fold Door hardware that frequently has to be able to carry loads of up to 800 kgs of glass in BOTH a sliding and swinging motion!