A website or domain is not a business, so the normal multiples you are citing don’t apply.
Now if you were to include the affiliate accounts associated with that site and all exisiting players at each program then the case could be made for the formula you used. I doubt you would/could do this though.
Generally when someone purchases your site and or domain its limited to the artwork and design that is there and the domain itself. You retain ownership of your affiliate accounts and players.