Well, I haven't heard back from e-on on this, but I did go to both UPS and the US Postal Service, and the price is pretty much right on for a package of that size. Now, I suspect there are discounts for volume shipping, etc, but I'm not sure there's much which can be done.

FWIW, the book is printed on gloss paper with an ultra heavyweight stock for the cover. It's a nice print job and sending it only in an envelope would probably do damage to it. 

If anyone has any ideas, I'm all ears.