Website value is so subjective there is no easy way to answer that. It is more an intrinsic value in most cases unless the site is a strong revenue producer then you would take annual income and figure how many years out you would want from it and pay that amount.

it's not like it is an actually viable product either. I mean one day it could be the new hot thing and the next it could be a desolate wasteland and there is nothing at all to show for it except some code and memories.