What is reasonable price for 2001 S

[tn0]

Hi,
new to the forum and not yet a Porsche owner. I found a 2001 S with ~40k from local private seller, after test driving it I had PPI done yesterday. Left CV outer boot torn, but other than that the mechanic said it was about as clean a car as he had seen from 2001. I reviewed the service records, owner (and previous owner) obviously taking good care of. The IMS has not been replaced, but the mechanic pulled oil filter and found no indication of trouble.
My only issue is this - seller is standing firm on price and I think he is asking too much. He listed for $15k, after PPI he is willing to sell for $14.1 as-is so he theoretically came down a little bit.
So I have looked at KBB and NADA Guide, KBB says he is asking $4k too much and NADA says about $2k too much. Any advice on whether I am a sucker if I bite?