I recommend scouring the local used gun racks...
I usually see one or two older beat 700s with lousy scope mounting jobs and cheap scopes for about $400 when I go gun hunting... You might be able to make a deal... Mind you, you get the stock too... I understand M700 SA actions alone go for $400- so anything cheaper than that you have to jump on. For a while there, you could get the Synthetic Youth M700 in .308 for $369...
I feel the older M700s are more square, better machined, and drilled and tapped straighter therefore more desirable unless you're going for a total blueprint job...