New production Springfield rack grades go from anywhere between 1100- 1700 depending on the model. Check gunbroker for comparisons before you buy.
Older models sometimes go for less, sometimes more, depending upon the condition. Check M14forum.com and there is a dedicated subforum for researching value. If you get the serial number, you can sometimes learn alot about the rifle. Also estimate number of rounds fired.
The early models are generally composed more of USGI parts but you want to make sure the barrel wear is ok. Even if you don't have gauges, at least take a flashlight down the bore and check for throat erosion or chrome flaking and the muzzle erosion.
Look how much wear on the bolt, op rod, op rod channel, etc. Check the bolt face for pitting/wear, and check the firing pin for roundness/wear Tilt the rifle back and forth a few times and listen for the piston to move about the gas cylinder.
Check for manufacture of parts (bolt, op rod, trigger group). Pull the trigger group if you can. Check the trigger housing splines for peening or any other mods.
Check the op rod spring guide, especially the mag catch portion for wear or damage. Check the front sight for alighnment. It may be off a bit in the dovetail, but as long is it is not overhaning it is fine/cosmetic. Check the rear sight - standard or National Match/peep. Hows the stock? Wood - walnut, birch, other, fiberglass? bedded? Lots more but my fingers are tired.
Good luck