How much shoul I pay for this 67 convert?

[skinnyboy67]

Stopped by today....again "8 years later" to ask about this lonely convert.
This is what I do know:
Last registered in 1976...then it sat in its current state.
40k orig miles on it.
1 owner car.
Complete car......interior....engine....top....rear.....all matching numbers.
It is not a rally or super sport.............just a 67 rag top with a power top (yes power top...i can see the cylinders)- 350 single barrel- automatic
It needs every panel of sheetmetal..........cant look at the floors.....but I can only imagine.
I currently have 2 other 67's...so I know whats involved in the restoration.
I just was wondering what others thought would be a reasonable $$$ amount to the owner, because my $500 offer didnt sway him too much.
Would love to have some opinions.
Thanks