Jeff,

I am going to give you the answer of the son of a professor of statistics and probability. You said it your self below...essentially, we don't have a big enough sample to be statistically significant.

: We are dealing in rare watches, resulting in a very thin market,
: so it is often difficult to estimate the “fair market value”
: of a particular watch.

All we can do is speculate. My relatively educated speculation is that goods generally go for over the market value when more than one person with buying power is interested at the time of the sale. Goods generally go for less than the market when only one person is interested.

You just never know what will generate interest.

JohnCote