CDNN's A2 uppers are a smoking deal, but you have to figure in the $10 postage, and that they don't have any of the parts to build the upper in stock. So you're looking at another $40 or more for the sights (flat top A2 sights are different), $15-20 for a cheap port cover and forward assist, plus the shipping for both from another vendor - call it about $10. Pretty quickly you're at about $120 just for the upper receiver parts that still need to be assembled.
A good, new 20" government profile A2 barrel with 1-7 twist, chrome lined, with the front sight base installed is going to start around $250. If it doesn't include the muzzle device, crush washer/peel washer, sling swivel & rivet, sight post, detent, and spring, you can add another $20. Figure $10-15 for a gas tube, another $20 for handguards, $10 for a delta ring assembly... Then are you going to reuse a bolt carrier from another upper? If not, add another $80-100.
I'm not really seeing how a person could build a real A2 upper half for less than about $500 without resorting to used parts, or cutting corners (1-9 twist, non-chrome, HBAR, etc). That also assumes you already have an upper vise block, barrel wrench, torque wrench, punches, hammers, etc.
Has anyone gotten an A2 upper from Model 1 recently? A year ago when a buddy was looking for one, he put in his order and they didn't actually have any A2 uppers on hand. Even though he ended up with a flat top it seems like a decent quality rifle.