With a few connections I paid very little more than a moto for my Lonestar{everything they make} CRF450 quad. Including Custom Axis ZPS all the way around. I'd sell it for 15k and build another one.

 

MY quad can be built for less than the price of a Moto. It will not have as top notch shocks as the Moto, but it will be a Honda and we all know how well they hold up.
This way isn't the best way to go for everyone however as you do have to have a 400EX or 250R as a basis.
If you are a Honda fan, build you a CRF and if you're not, buy yourself a Z400 or KFX400 to modify the way you like it,OR buy a Cannondale Moto and hope that you don't experience any problems with the complicated computer system on it.
Whatever floats your boat I guess.

Captain