a few qusteions about some autographs i think i would like t

[miley cyrus fan]

ok guys i have a few value qusteions and other things about some autographs i would like to obtain.
the other day i saw a alexis bledel and lauren graham duel signed autograph it was in a glass display case and i did not ask the casheir how much its going for but i may go back to that store tomorow or sunday if its still their whats the most i should pay for it?
also does anyone know wheir i can a autograph of the late rick danko
and yesterday on ebay i saw a autograph of the late harry chapin autograph it was in a album already i am pretty sure its glued on its on a piece of paper the autograph it has a few pictures of harry signing but i am pretty sure no certificate because it was obtained at a outdoor concert the starting bid is ten dollars does anything i just mentioned lessen the value if so by how much.
also wheir can i obtain a don henley or miley cyrus auto miley has a pretty good ttm record but still i wouldnt mind a bought one first so i know i got one but a personalized ttm would be nice and don has a terrible track record it doesent make me any less of a fan of him or the eagles but still.