Well, at least you did the right thing. Not so sure it was the smart thing, but it was right.
I never test them when I go pick them up or offer advice in advance. I pull the glass and lift the playfield, then pull the backglass to make sure all of the parts are there and the condition of the MPU board, then load that thing into the truck.
If he's only pushing it on CL then I still don't think it will sell. Let him sit on it a while and then call and offer him several hundred less for it if you're still interested in it.
Games usually don't sell well here, and when they do then it's for a very low price. I can barely sell arcade games here for $10 - $50 non-working. To give you an idea of pin pricing in the area, I got a Jurassic Park for $15, Doctor Who for $100, and Judge Dredd for $300. All were not working at the time, but that's still insanely low pricing. I've seen working EM's not sell at $200.
Anyhow, let it set a few weeks and then make him an offer on it.
-JM