I've actually seen a few tempting buys on BCGs on,,,gulp...GunBroker of all places. They've had the cerakoted M16s (The STS ones, from the looks of em) starting @$175 and with a Buy it Now of $200.
If they are the STS bcgs, that's a helluva solid BCG. I'm running them in a couple of my guns. They're slick as snot and make for a really smooth action.