Value of an Old Dictionary?

I'm trying to find out a price for this Philadelphia School Dictionary of the English Language, that I have by Benjamin Johnson 1805 that is a first edition. I have come to a standstill on my search. It has led me to only three libraries that hold the dictionary. I was just wondering if anybody has run into this dictionary and knows of any of the books by this author and what they sold for.

Thank you very much.