I got a Service Grade USGI M1 Garand in either 2004 or 2005 (can't remember) and was very pleased so in early 2006 I got another Service Grade M1 Garand (this one was a Greek-return) and it was in even better condition than the first one. I've gotten a few offers to buy the second one (including a standing "if you ever, ever decide to sell it at anytime down the road. . . ) but I always just refer them to the CMP so they can get their own.
Maybe this is not the best method of comparison, but I've looked at what they ask for at the local gunshows (dunno if anyone actually pays these prices). I got both my Garands for $500 each from the CMP. In similar condition at the shows, I see something comparable to the first one priced at $750-800 and for the nicer Greek-return, $950-1000. With the gunshow guns, I don't know about barrel condition. Put me down as a happy customer as I sometimes think about getting yet another CMP Garand, but actually I could use a new shotgun more. . .