1970 duster value?

I can tell you that I paid $2500 for mine and it sounds like roughly similar condition to the one you are looking at. Here in NY, $2500 is a STEAL for a car like this. In the rest of the country, not so much.

My car has a lot going for it though. The interior is like 95% perfect, it is missing an armrest and has a tear in the seat but besides those two issues the rest of the interior looks brand new. The car only has 53,000 miles on it (52 when I bought it), and I bought it from the nephew of the original owner- who was a 53 year old woman when she bought it in 1970! She gave it to her nephew just a couple years ago and he just stored it in a garage at his business until he decided to sell it. The car came with the original sale papers and a lot of service history.

Taking all that into account, I would say that a car in similar condition, outside of NY, and without the history, should be available for under $2500.

As for my car... $2500 would not even come close to separating me from it. My cars are worth more to me than they are to anyone else.