[SJSAMPLE]

But I can buy a lower for $150, stripped.
An upper may be worth $300 to $800 for a standard configuration, depending on wether a bolt is included.

[Condor51]

But I can buy a lower for $150, stripped.

Wouldn't know, never shopped for one.
All I've ever seen advertised for sale as to parts were 'Uppers'.

Don't have an AR-15. Don't like the 'little bullet'.
If I had the extra funds, it'd be an AR-10 (.308)