I paid $2,000 for my XL frame a couple of years ago, and it is still going strong. It is a quality carbon frame. With a top of the line XX1 build and Easton EC90 wheels it weighs 20 lbs even. In the fall, this frame does double duty as a cross bike, I throw on a rigid Niner carbon fork and lightweight tires and it weighs only 17.5 lbs, which is actually lighter than my carbon/Ultegra road bike.
I suspect that there are a couple of reasons why this frame is on mega clearance: first, the big XL size doesn't fit many people. It fits me great, I'm 6'3" and 180 pounds. The second reason is that I suspect that very soon Niner will be updating this frame to the 142mm rear axle standard. This may not bring any weight savings, but will be an update to fit in with this trend of the marginally stiffer 142mm thru-axle. I will be riding this frame for a few more years before seeing any need to upgrade, it is holding up great.