Well you'll notice I'm not buying it, I wouldn't pay that much for that particular watch... but the market value of the WM9 v2s has been shown over and over on the various rep forums to be closer to $700. They sell for $675-700 all the time, typically within hours.
The PT / Supreme (which is/was the same as the WM9 v1, not the v2) is a pretty nice watch. But last I heard, a "lot" cheaper was still $400+ and you don't get the WM9 dial/hands which have superlume.
The WM9 v2 has the higher crown position (doesn't matter to me, but a big deal to some) and it's a matter of opinion whether the v2 or the v3 was the better watch. However, it's basically unarguable that one or the other was the best Sub rep ever made.
WM9 is gone, so if you want one you have to pay. That's how markets work.