I don't think Ed himself did any of the Ratfink drawings in 80's undergrounds. the Starhead Ratfink Comix were done by R. K. Sloane.
Unlike most 80s minis, the XEX Graphics books were mostly if not all offset printed, and often had heavy cardstock covers. $5 - $10 is probably a decent ballpark on value, but don't know how easy it is to find a buyer.
yes, the rat fink stuff is cool and r.k. sloane was his ghost artist. i love sloan's comic work and his paintings are great. he died about three years ago. BUT bagge's run on neat suff and hate are classic MUST READS.