Here's a web site that tracks collector values.  They don't have any 1981 data for some reason but 1982 would be close.  Notice the condition page too.

An auction that is well-followed by Z and ZX people is BringATrailer.com  Known as BAT.  Link below.  Might give you some ideas.

https://www.hagerty.com/apps/valuationtools/1982-Datsun-280ZX?id=124375

https://www.hagerty.com/valuationtools/Classifications-and-Conditions

https://bringatrailer.com/search/280zx/

I'm right in line thinking that this car is a solid $5000 - $6000 car in good condition. Of course, its worth whatever someone is willing to pay, but my bet is that it will go in between those two amounts. Nice car! Smaller market for collectors/enthusiasts still.

Thanks for the information.  I am trying to help a friend sell it. He was thinking 10k. Maybe he is thinking wrong.  I am going to see him tomorrow. 

Hey Darlene - I’m sorry im not interested in buying car but I am in need of door seals for mine. Do you have any spare parts?