This is a site where tractors and equipment are advertised for sale. I use it as a guide. If I see something in Tennessee for $2,000 I look up the same thing on Tractorhouse.com. If I find a similar model age tractors or equipment in the range of $2,000 I assume it is worth $2,000 then I look into condition. If I find a similar tractor for $4,000 I ask why is my local tractor only $2,000 and vice versa.
Hope this helps.
I assume there is a blue book on equipment but don't know where to find one.