Ron:
Just curious, and my comments probably can't be replied to publically, but ... I've worked in tech publishing of automotive street performance books, racing books, racing personality books and the like since the '80s. As writer, editor, contract negotiator, and sales in both hardback and paperback -- and $100 non-discounted retail is a stout price to ask of a specialized market like consumer audio (the upper end of it, too) , and even so in the larger specialized one of car/racing enthusiasts. The work has to be extraordinary to command that price.
I can think of a few reasons for the $100 price --
Very limited press run of say 1000--2000 copies? Hardback cover on the book, and comes in a hard, Mac-logoed, leather-embossed slipcase? (Some consumers expect that at this price point.) Signed edition by key Mac personnel? Had to pay the author a huge advance? Going to be 800 high-quality paper pages with 1000 color images? Mac is making $50/book <G>? You all are self-publishing and don't have the economy of scale a large publisher (say Motorbooks International) has, and have to pay higher for editing, production, and distribution? You're not having it printed in Hong Kong and using a specialty publisher in the U.S.?
Please don't take all the above as critical, but if I had a retail price of $100 to work with, I could publish quite a double-throw down tome on racing cars/people. Given the Mac brand's audio credibility (I'm thinking Porsche or Mercedes-Benz here), I can see wanting to produce a high-quality piece, but that price point will cause the specialty consumer to pause in my experience. YMMV, and I hope it does. Good luck with the project. It's not as easy as some might think!