If it's not going to help or make me take better photos, I'd be loathe to pay much, if anything, extra for a camera used by someone famous. The other thing is that, dependent upon who owned it, the camera might be absolutely battered if it was a professional tool and might end up being no more than an expensive ornament.
I would, however, like to own some photos taken by someone famous. I saw some beautiful prints of photos taken by (and printed by) Dorothy Bohm a while back. I would love to own a couple but they were upwards of £1,500 each; so I'll have to make do with her books.
Incidentally, for those interested, there's an exhibition of over 100 of Ansel Adams' prints to be shown in Greenwich from early November. Lara and I will be there one weekend. Anyone interested in meeting up for the exhibition / day shooting in the area?