Quoted from Eric_S:Star Trek premium is a great game. $7700 seems a bit high and $250 for a project Bally Star Trek seems a bit low. $7K total including shipping would probably be reasonable, at least to me.
I was thinking this as well, but it gets really tricky when you are pricing trades. $7700 is their list price for this, but since they only have one they may not be willing to move off the price.
They will probably fix your old machine and sell it for somewhere in the $1250 neighborhood, or if its in bad shape part it out. If the backglass itself is in pristine condition, you can probably get $250 just for the glass.