how much for a standard DPMS AR15 A3 carbine (16inch bbl)?
what quality is it compared to colt and BM

Can't discuss the cost issue because I've noticed that the AWB sunset has triggered a feeding frenzy for 'post post-ban' ARs here in the Atlanta area and the marked prices may be a little high.

As to the quality of DPMS ARs?  I have a 20" HB model (post ban, without the eeeeeeevil flash hider or bayonet lug).  Forged upper and lower.  Quality of the finish is on par with the Colts and Oly's I've looked at, i.e., it's pretty darned good and the upper and lower match perfectly.  The fit is quite good - fully on par with the competition.  I carried various M16s for 20+ years, so I know what I'm looking at.  So far it eats what I feed it with no complaints, and the bullets go where I point them with great regularity.  The only FTF issue came with the 'give-away' British made 30-round magazine.  If I fully load the mag the rifle won't strip off the first round.  This is a mag issue, not a rifle issue.  I have a miscellaneous collection of 20 & 30 round issue magazines I've collected while in the Army and all work just fine (Believe it or not, after coming back out of Kuwait after Desert Storm the unit armorer told us to keep our magazines or toss them before we left Saudi!  Seems he got a complete re-issue of NIB 30 rounders and didn't want the 'old, nasty, used ones' back.  Mine went right into my ALICE pack for future use.).  My only complaint about DPMS is that they don't chrome line their barrels as a standard option.  They do offer them, but you pay extra.  Bottom line - DPMS makes a fine rifle and it's well worth the $$$.

BWH