Nacho, I reckon it is like Real Estate. The value of a property accounts for required renovations and repairs. A website SEO and Architecture is the same. A site that needs drastic repairs is devlaued.
One that is good to go is worth a bit more than one that needs a major overhaul. As with real estate, this is a % factor, rather than an absolute value. So, a site in a good "Location location location" and great SEo and architecture is a good buy, but one with bad SEo and Architecture in "Location location location" is still better than a great SEO site with very little else.
So, thy are worth nothing by themselves, but multiple (2-10 times or 0.1 times) the other values.