$40 would be an impossible price with 600 sold copies. Well, perhaps doable if he could sell those copies pre-publication. As for Mosrten's book, I have not seen it, but the specs (format and page count) are quite close to this:
http://www.amazon.com/French-Battles...5831818&sr=1-1
Note the cover price of $74.95. And USNI is a big publisher for a specialist publisher.