How do you guys determine price value?

Hi, I’m interested as a buyer, how do you come up
with the value of each vehicle? It just seems some
of the same vehicles are valued higher than one
that may have the same options and condition with
maybe less miles. Also I not sure why, I’m thinking
it’s to help fund the site which is totally fine. What
I’m talking about is the likes of KBB, NADA,
Edmonds on trade in or get cash offers, I think
that’s one. But I have been in the market looking for
a truck. I have been to several dealerships. When I
put my info into one of these sites I’m getting back
20k-24k. I have used both good condition and very
good. I went to a major dealership in MA. And they
started off at offering me $13k. Now the other
dealerships were starting right around $17k.
Depending on what price range I was interested in
for my purchase. The MA dealership, went up to
around $17k if I were to purchase a $40+ truck. If I
interested in the $35k truck then it’s down to $15k
or less. I know I might rate my truck value more
than they are, but there is no way my truck is only
in fair condition. This dealership was giving me a
trade in  value of a poor condition truck. I know this
has nothing to do with you guys but looking at what
KBB and the other, it seems like there estimates on
value are pretty far off. I’m going to go on there
sites and ask them the same questions. Hopefully
they can help me understand there evaluating. All
and all I really enjoy your site and appreciate what
you guys put into it.

Thank you
     Joe Lister