oh stats just base it on visitors and presume you have ads on your site.
Although RG does have ads on it, a lot of the daily traffic don't see that one as they are upgraded.
for example it valued my work site at like $2k and a daily income of $20 but really, it makes no money but due to the amount of traffic they presume that.
hence the lower buy price.
it can also under estimate, for example it values google at like $2b but only a daily revenue of about $3m not taking into account the way google works with bids and shit therefore making the daily revenue more than $3m.