As far as I can tell there are a few tiers in the AR lower market:
Lowest and to be avoided: Hesse/Vulcan Arms
$85 - $100 stripped and higher than normal variations in machining: Olympic Arms
$100 -$120 stripped, less common but decent quality: MEGA
$110 - $120 stripped, good quality ("Honda"): DPMS, Stag, Bushmaster, Double Star, CMMG, RockRiver (complete lowers will be $250 - $300)
$130 - $140 stripped: top quality: LMT, Noveske (complete lowers will be $330 - $500)
The stripped lower is pretty much the same from the $120 - $140 levels. There starts to be some differentiation in the lower parts such as the triggers, etc. The real differentiation in quality is in the uppers with barrels, bolt carrier groups, sights, charging handle, and handguards.