I would call him back and tell him, it is worth $3500 to you. I can't see if it has insert wear in the pictures, but if it doesn't that would be my offer. Tell him that is all you will pay and if he wants ebay / retail prices look elsewhere. If he calls you to come get it after a few weeks NP, go get it. There is no line forming for dirty poorly maintained pinballs at retail prices of any title.
Talk is cheap and people who call CL sellers to offer over the asking price almost never show. Or when they do they offer to pay less...
-S