BTW, how much is one in 5.56/.223?
About $1200-$1500 usually but that's because we're talking about no longer made collectible rifles versus mass produced AR15s. If the AR180 were made by as many makers as the AR15 is I suspect it would be cheaper than the AR15. Here's a great listing for one from each maker; ArmaLite, Howa and Sterling. ArmaLite reintroduced them a couple years back with a plastic lower but nobody really wanted one with a plastic lower.
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=460642829