What does everyone think would be a fair price to offer on this machine?

Difficult to say.. new BG and PF throws a spanner in the works. They are NOT LED displays as listed.. they are original neon displays.

Back box has been badly drilled out by someone who doesn't know what they are doing.
Normally for a good FP.. bit of flaking on the BG ( all have this)...original PF id say around $1400 in working condition.
Its NEVER a $4K machine even with a new PF etc.. no one is going to pay that for an FP.
Throw a PF and BG into the mix and top price id say would be in the region of $2400... any more and you'd be doing yourself a disfavour IMO