I looked around and the cheapest I found is $525 on Ebay. The seller is not offering shipping and is in Fairfield, CA. You have to pick it up in person. I don't think I've ever seen that before for a book on Ebay. I suppose the seller doesn't want to deal with insurance which is problematic for collectible books. He has refused an offer of $325.
I have two copies available, both of the second edition which corrected a bunch of typos that were in the first and has a little added material. They're both in like-new collectible so probably more expensive than you were looking for. I'm asking $450 for the less expensive one. The more expensive one is from the numbered limited printing (32 pairs of W1P and SM&S) in a special gold-colored leather cover with signatures of the "co-authors". I'll only sell it with the matching SM&S.