Yeah, Spikes are nice ones.
Most AR lowers are of equal quality, though some have features that others don't.
Most common brands range from about $60 to $120(non-billit, those are over twice as much). It all depends on what you want it to say on the sides.
Looking for a particular brand or features?
EDIT: If you
are looking for a billit-style lower, I suggest talking to Scott over at Reaper Arms in Shelby, NE. These things are wicked and look to be of excellent quality.
http://www.reaperarms.com/Default.aspx