Why does it have to fold?

Can't remember ever seeing any viable off the shelf folding full suspension MTB's, only cheap ones like this, which would not survive a good day off road. You can get some hardtails, like the Dahon Flow, but these cost a lot, there oneon Amazon for $2500. You could get a regular bike converted with S & S Couplings, if it was steel, and there are not may Steel suspension frames arround; again these cost alot.