Why don't you just send him 1 or 2 sets like a previous poster said? If you have 11 sets, it should be no big deal. I agree with Peter also. You need to diversify and sell this to a few different folks to maximize your profit. Any dealer buying 11 of the same sets no matter how nice they are, is thinking "diminishing returns".
You really can't win unless the sets are NM or better which for 1971 would be pretty rare for obvious reasons.
Split them up amongst the hobby for better profits and a happier collecting community!
Peace, Mike
PS By the way, what is the "average" condition? I would accept a set on approval basis if you are interested in shipping to me, let me know.