Be careful of getting a false sense of a book's worth by the pricing you see on Abe Books, Amazon etc. Princeton Antiques of Atlantic City is notorious for its insanely inflated used book prices, and their listings are everywhere. Hopeful con-artists on Amazon are selling Heart of the Pines for 300 dollars, apparently in the hope some unsuspecting soul will think this is a rare book and out of print.
The list price of this book new, as sold by the Batsto Citizen's Committee, is 60 dollars. How much a signed used copy is worth depends upon how many signed copies are out there, and how much someone is willing to pay.
This massive work, with over 900 photographs, is a bargain at 60 dollars, so you should certainly ask for more than that for a signed edition.