Good question... IMHO and from what I’ve seen of past sales and previous posts 80s and 100s prices are mainly driven by:
A) Rust Level
B) Maintenance
C) Mileage/ Accidents/Title/ Owners
D) Equipment
E) Interior and Paint
F) Factory Lockers
G) 40 Anniversary edition
A & B are the main purchase drivers. C-H are secondary to A & B and increase or decrease the price for up to 15% EACH and are usually not a deal breaker ( individually) if A and B are ok.
Based on that you can assign values as follow:
1) A&B each are measured on a scale from $0 to $ 5k.
0=neglected $5k perfect condition
2) C-E increase or decrease price by 15%
3)F-G only increase price by 15%.
As an example of how the scale would work:
Example 1) a perfectly maintained, rust free 80:
A) Rust Level: No rust = $5000
B) Maintenance: to date with records. $5000
C) 200k miles/ Clean Title (15%

). $1500
D) Original Bumpers no lift (0%

). $0
E) Interior 8/10 Paint 7/10 (15%

). $1500
F) Factory Lockers (15%

). $1500
So theoretically a 200k mike clean 80 should be around $14.5K.
Of course there is the “must have” factor, the extra equipment (I.e roof tents) the specific year model, color and the time capsules and unicorns, which are out there and impact price beyond scales and possible measurements.
And now we have access to foreign 80s, making the hunt even more interesting and price appealing.
Those are my 2 cents.
Thoughts?