I sold a Mamiya 7 body in mint condition with the caps, strap, even the original sales receipt on E*ay a little while ago for $465. Ouch. I had many dazzlingly well lit photos, a full description, everything I thought I needed to get a decent price. And it was bought by a guy in Europe. So it goes.
Then last year I sold an Aero-Ektar lens that cost me $150 for $480. Some you win, some you lose. I figure it evens out in the end.
With the Mamiya/Leaf partnership we may see digital backs for our Mamiya gear sometime in the next decade. Will we be able to afford it? That I'm not so sure about.