I'd say the value is what you see them going for on Gunbroker. If you want comparison to a new gun, the Trailside is being imported by Hammerli as the Xesse, and those run for $750 for a 6" model. Pretty much the same gun, just different grips.
http://www.larrysguns.com/Products/H...-Standard.aspx
Trailsides didn't sell well but now it seems they've finally gathered a rep for being fantastically accurate guns (my 4" model shoots like a laser gun... if you miss, it was you). The prices seem to have risen accordingly.