To give you an idea of mine...
Stag lower $120
LPK $80
DMPS Complete Upper (BCG, Charging, Chrome 1:9, .223) $600
Pre ban 30rd mags $14ea
I'm swapping my bbl (shown in the pic posted earlier) for a post-ban legal one and should recoup a few dollars once I sell my 16" w/ flash supp.
Just need to swap the new bbl and install a rear sight and I'm good. Like Jordan said, as time goes on and I become more experienced with the rifle as well as hopefully get more hands-on experience with others' rifles, I'll start shopping for some of the optics choices...which can be pricey. Than and I'd like a quad rail fore-end...so I can mount one of these...
http://www.youtube.com/watch?v=3ljd_hUxCfI