Sorry, it's not my offer, and I'm not setting the price.
If you're interested in finding out more about the back I'd be happy to put you in touch with the owner.
I know the back, have used it, it's in perfect condition.
The e-bay seller you link is selling an Imacon back with the H2, not an Aptus 22
They're not even so sure which back it is, or if it's a 22mp, saying in the listing:
"Lens looks clean and clear - no dust, scratches, or fungus
Aperture blades look clean
Shutter sounds strong
We believe that it is 22 MP"
The back I know is in NYC
Where are you? UK?