Quoted from Pin_Guy:

This machine was kept in a damp environment for a LONG time ... I can only imagine how musty the cabinet smells
My thoughts are this:
I like that it has all original boards although the CPU is done for.
The playfield appears to be in fairly good shape, I don't see any ghosting around the shield inserts which is common for this game.
This game is going to be a corrosion nightmare, most of the upper playfield parts are stainless so will clean up pretty well, the underside is a different animal and the lamp sockets are going to be very problematic as once corrosion gets in them the only real fix is replacing them.
Since it doesn't boot, you have no way to know what all is wrong, you will need to get the game to a working state BEFORE you begin the restoration so you can find out what all you have to fix during the restoration as well as know what stopped working because of the restoration.
IMO the current owner paid way too much for it, I would be hesitant to purchase it at all without seeing it in person, and even then assuming I didnt find anything not in the pictures, I wouldn't want to spend more than $2500 for it in its current condition and wouldn't spend more than $2800. I wouldn't be surprised if it cost you at least $2000 ($3000 if you replace the playfield) on top of what the machine cost you to restore it to new condition.