Sorry to say, but you paid FAR too much for that book at $399, especially when SS 9.6 copies signed by McFarlane and Liefeld are selling for only a few bucks more, and single signature 9.6s are up to $100 less.
Unfortunately, the "premium" you're now seeking will likely be impossible to attain any time soon:
1. You already paid the premium, and them some.
2. It's a modern age book, and only a 9.0. 9.6s and 9.8s are plentiful.
3. The signatures look absolutely garish in relation to the cover,
No store with any modicum of sense will give you anything close to what you paid, and I doubt any collector will either. Chalk this one up as a lesson learned.