Wow! I have a Filmore West poster that I bought about 18 years ago. The bill lists:
Jr. Walker and the All Stars
Fleetwood Mac
Lee Michaels
Tony Joe White
August 5, 6, 7, 1969
I know I paid less than 70 dollars for it -- in mint condition! I bought it at a record convention, where I also got an original, very rare 1967 Monterey Pop Festival poster for $300. I had both professionally framed and they hang in my living room.
I recently saw a Monterey poster listed for $15oo! I'm not into fine art, or art as an investment, but I think I made a very smart purchase!