This article is pretty old (2007), but the story it tells is never-the-less very interesting.
Basically it turns out that big name companies like Patek and Omega put their own watches to auction - only to buy them back at inflated prices. The purpose of which: To rig the whole market so as to create an artificial inflation in the second hand value of their watches.
I do wonder if this practice is still going on, and to what extent it is legal at all? I certainly doubt that it would be in the UK, but perhaps Switzerland is different.
http://online.wsj.com/article/SB119178753176051433.html?mod=hpp_us_pageone