AR parts are parts... the only difference with the Colt Big Pin rifles (and I have one...) is the fire control group and the receiver mounting pins. Other than that, pretty much everything else is AR. Mine doesn't have the sear block, though.
There are ways to get rid of the sear block (I don't belive it is illegal, you are not modifying it to be full-auto or anything) if it becomes an issue. If it's an H-Bar, it's probably just as accurate as my H-Bar... it's all in the barrel.
I would think the value would be less than a non-sear blocked AR, that really limits you on using just the Colt BCG. If it's really that new, I would think $500-700 range.