$559 + your local ffl transfer fee. I'm not sure what shipping would cost.
Del-Ton AR-15 M4 COMPLETE Rifle Kit [DTI-15] - $559.00 : Cold Hand Arms, From our COLD DEAD HANDS
Maybe this is just me, but I like to have as many parts on my guns match as possible. I also think it's going to help the upper and lower fit together a little bit better also. I'm trying to find the best deals on a del-ton lower as possible, but the best I can find is about $100. It's not that much more than the dirt cheapest stripped lower out there is I think it'll be worth it to have more parts coming from the same manufacturer and hopefully having closely matching finishes.