In my part of the country (central Illinois) you can expect to pay $1000 to $1500. My wife did buy a Bushy with less than 100 rds. through it for $600, but you will wait a while to find a fool like that (in this case ex-LEO). I just found one a few weeks ago for $1150 (Colt made in 1974). Last year a cherry Colt made in 1981 could NOT be obtained for less than $1500--but I wanted it BAD. Always keep $$ available and keep your ear to the ground. They are out there and do pop up now and again at a good price. Definitely haunt the gunshows. There is a reason our enemies want them gone. One of my best friends just bought one last month off a guy's table for $575--DPMS parts gun, but very nice shape. The guy had just bought an M2 (YES, a real Ma-Deuce!!) and said the "poodleshooter" just wasn't fun any more. [BD]
Edited to add: Associate yourself with other shooters. Most of the ones to be found will be referred to you by others once you have quietly put out the word you are looking. Join shooting clubs, collectors groups, local range leagues, hang at gun shows, hang here at AR15.com, you get the idea. Associate with good people and good things will come to you. [:D]