I agree, which is why I bought six when they were $115
But…
$190
Bolt – Case hardened 9310, shot peened, magnetic particle inspected, with high-performance extractor, ejector springs, gas rings and special O-ring buffer. NiB-X Black coated. Firing Pin – Manufactured, heat-treated, hardened, chromed and certified per government drawings. Carrier – AR-15 or M16 style (heavy weight), 8620 material, heat treated and case hardened. Manufacturing tolerances on inside diameters tightly controlled. NiB-X Black coated for durability and ease of cleaning. Gas Key – Hardened to USGI Specifications and attached using grade 8 hardened fasteners. NiB-X Black coated. Staked per military specifications. Cam pin – Manufactured, heat treated, hardened and certified per Government drawings. NiB-X Black coated.
https://wmdguns.com/product/ar-15-m16-m4-full-auto-bolt-carrier-group-nib-x-black-nickel-boron-polished/
vs
$140-170
Bolt:
Precision machined from Carpenter Technology No. 158 alloy,
Heat treated per mil-spec,
Shot peened per ASTM B851/SAE AMS2430S,
Vibratory tumbled
Individual high pressure/proof (HP)
Full Auto test fired as an assembly
Individual magnetic particle inspection ASTM E1444/E1444M (MP)
Markings deep laser engraved (SP=Shot Peened, HP=High Pressure Tested, MP=Magnetic Particle Inspection.)
Extractor:
Precision machined from 4340 tool steel alloy per SAE AMS6415T/AMS6484D (vs 4140),
Heat treated
Shot peen per ASTM B851/SAE AMS2430S.
Extractor Retaining Pin:
Precision machined and ground S7 Tool Steel
Heat treated per ASTM A681-08
Shot peened per mil-spec print
Manganese phosphate
Extractor Spring:
Tactical Springs/Sprinco 5 coil, ASTM Grade A401 Chrome Silicon wire stock
Heat treated
Stress relieved, Molybdenum-Disulfide infused
Cryogenic processed (all post winding)
Mil-spec black insert/synthetic elastomer extractor buffer (nitrile-butadiene, shore hardness 80+/-5 durometer per MIL-PRF-6855)
Ejector:
S7 Tool Steel
Heat treated per ASTM A681-08
Shot peened per Mil-Spec
Manganese phosphate
Ejector Spring:
Heat treated
Mil Spec
Gas Rings:
Standard stainless steel per Mil-Spec X3
Carrier:
Machined from AISI 8620 aircraft qualty alloy per ASTM A108/A322-13
Full auto profile
Heat treated
Carburized/strain relieved, hard chrome bore
Precision ground gas key interface
Sons of Liberty Battle Flag logo deep laser engraved
Manganese phosphate
Gas Key:
Machined from 4130 chromoly steel alloy per ASTM A108/A322-13
Heat treated, hard chrome internal
Manganese phosphate
Permatex sealed
Grade 8 hex screws torqued and staked all per mil-spec
Cam Pin:
Precision machined 4340 chromoly steel alloy per SAE AMS6415T/AMS6484D
Heat treated/processed per mil-spec
Manganese phosphate
Solid film lubricant applied and cured per mil-spec
Firing Pin:
Precision machined 8640 steel alloy
Heat treated/processed per mil-spec
Hard chrome plate
Firing Pin Retaining Pin:
Precision machined from 1038 carbon steel
Heat treated/processed per mil-spec
Manganese phosphate
https://www.primaryarms.com/sons-of-liberty-gun-works-m16-bolt-carrier-group-223-556-phosphate
= not even close