Hi Ping,
I mean no disrespect when I say that the Bulgari's in Elizabeth Taylor's collection are not representative of what the watches will do at auction under less fevered circumstances. More than just buying a watch, people were buying a legend, a piece of Elizabeth Taylor. How often, if ever, does one get the chance to own a piece, whether clothes, jewelry or watches, from an icon who lived life so much in the public eye.
I think if you look at Bulgari in a more usual situation you won't see such spectacular results. In fact, sad to say, like most brands, the value isn't there after it leaves the AD.