Yes and no.

PSA (Palmetto State Armory) has blemished receivers for sale for $50 regularly.


Stick with the aluminum receivers.
With the exception of the Carbon Fiber sets, the poly receivers have a number of issues.

There are only about 15 actual manufacturers out there, receivers that is.
The rest sub-contract from the others for the most part.

Here’s a partial list from 2006:
Manufacturer (then) manufactured for
Brands by Manufacturer (all manufacturers require an ATF Variance to allow a contractor to actually have receivers produced by another company):

LMT = LMT, Lauer, DS Arms, PWA, Eagle, Knights Armament, Barrett, Bushmaster (?)
CMT = Stag, RRA, High Standard, Noveske, (new) Century, Global Tactical, CLE, S&W, MGI, Wilson Tactical, (some) Colt, Ratworx
LAR = Grizzly, Bushmaster (L Prefix), Ameetech, DPMS, CMMG, Double Star, Fulton
JVP = Double Star, LRB
MMS = Mega, GSE, Dalphon, POF, Alexander Arms,
Olympic = Olypmic, SGW, Tromix, Palmetto, Dalphon, Frankford, (old) Century
Sun Devil = Sun Devil forged billet receivers
Superior = Superior Arms
Grenadier Precision