Value of the New Encyclopaedia Britannica?

I have a mint condition set of the New Encyclopaedia Britannica in 30 volumes. It is the 1984 15th edition. I'm not sure if the binding is leather, but it sure is beautiful! I was wondering if anyone new what they might be worth.

All of the volumes have black covers and binding. (I have seen online colored volumes, but these aren't.)

By M M