Value of Academic American Encyclopedia

i have a full set (21 volumes) 1990 Academic American Encyclopedias with the 1991, 1992, 1993, 1994, and 1995 year book updates. I also have the Index book. It has never been used. There is not one tear, folded page, etc. They look like they have never been used, which is the truth.

By Tracie H.