I agree that the "face" value of the books is between $4000 and $5000. I also agree that the dealer's 40% discount is a bit steep.
Unfortunately for you though, the market for the proofs seems a bit down at the moment. Geemann1 has had a lot of proofs on eBay recently (admittedly at a fairly high starting price) and very few have actually sold.
Best of luck!
John