It's a cool display piece, but the Gaston and Borders signatures are virtually worthless and the Carter one on it's own might fetch ya 15-20 dollars. The only one worth any money is the Robbie Alomar and even that you could probably pick up for about 50 dollars.
All and all, you might be able to get 100-125 dollars out of it because of the display appeal, but it's really not all that valuable of a piece.
Hope you find a buyer,
Cheers.