Yeah, +1.
Gunsmoke Lower (a company out of Okeechobee, FL who has their uppers forged from the same vendor as Spikes) - $69
Palmetto State Armory classic LPK with 6 pos stock & Buffer - $99 Total Lower cost $167 (You can also use the Plum Crazy complete lower for $125 for an even bigger savings.
DTI 14.5" M4 profile 1-7 chrome lined barrel with FSP & gas tube from Gun Broker - $125 shipped (These or similar are pretty easy to find on GB for anywhere from $100 - $150 but this build it was $113.74 + $10 shipping so I rounded up a bit).
Cerro Forge Complete upper receiver from Gunbroker $83 (I bought 6 a while back for $78ea + $16 shipping so I averaged it at $83 for 1, this is a pretty regular price because I just got 2 more for $78ea + $9 shipping the other day from a different GB vendor)
Barrel Nut & Delta ring assy. $10.50 (PSA regular price)
Flashhider $10 (We used a Phantom picked up from arfcom classifieds for $10 but if you can't find that deal you could use an A2 for $10 or less)
BCM full auto BCG - $135 (you can scrimp here but I won't. I do have a good source for a $99 full auto carrier that looks as good as the BCM though. I've got one in a rifle and it's doing fine with about 2500rds so far)
Mil-Spec forged CH - $15 (plans on swapping to a BCM Gunfighter for $45 soon though)
This give a build total of $545.50 - I had a Magpul rear BUIS I gave him so that saved him from buying a rear sight but you can pick up a decent used (or the ARMS that Magpul coppied) For $20-$25 with minimal effort. The only thing left to buy was mags and ammo (I gave him a old sling I had in my parts box as well) Botach has Lancer mags for $10 or a couple places have C-Products Mil_Spec contract style mags for $8-$9.
Granted I had all the tools and experience needed to put this together for him and I didn't charge any labor but he bought the beer and pizza for our build night. The good thing is he could probably just about build another rifle himself now or at the very least understands enough to properly maintain it. I'd compare the quality to being equal or better than any $700-$1000 retail M4 like the DPMS, Rock River, M&P etc. If you're really concerned about the brand I can find Doublestar lowers for $99 and just bought some Armalite lowers for $129 so another $30-$60 if that matters to you. I've actually used a few of these Gunsmoke lowers and never had an issue which I can't say for Rock River or DPMS, both of which I've had to make adjustments to the trigger or hammer holes or other issues.