I bet the venue would have a lot to do with price as well. For instance, I saw a History's Lost and Found on John Lennon's MBZ Wagon. When it sold at a John Lennon stuff auction in New York, it got a good price, but the dealer that bought it has had it on his classic car showroom, and not been able to get what he paid, if I understand correctly. His Pschodelic Rolls might be a different story, it is more associated with him in his prime with the Beatles, instead of some grocery getter he bought for his butler to use later on in New York.
Since you posted in the MG forum, I would have to assume that it is an MG and I am extremely curious about the celebrity owner.