Whether or not you are thinking of selling your 70’s movies, tapes or party costumes, you may be interested to know its value. You see, you have put in a good deal of effort and the original stories may no longer be on official record.
So go to price guides.and look up at least 3 of them.
Your next stop would be the Marvel Cartoon price guide.
An average value across these would give you a fair market price.

Markets are unpredictable and valuations can go in any direction, particularly if there has been something topical recently e.g. the release of a new movie or a Super heroes national convention.

If you do decide to sell, appear hesitant as if you were reluctant to let go of a teenage treaure.
Emphasise the old story lines and how they frightened or totally intrigued you as a teenageer.
Emphasise these are no longer available etc.

If you put a little thought into the words you use, you can make your offer much more appealing.