You can complete a build using the PSC-12 upper and JP's 6.5 CM barrel and head spaced bolt for under $3k. I did one for a buddy not too long ago. This is the parts list I told him to of get.
JP PSC-12 with BCG: $1100 (Mel dropped $100 off as he didn't include bolt with the BCG considering I had a head spaced bolt included with my barrel purchase)
6.5 CM barrel with matched bolt: $700
Shadow Ops Weaponry DPMS Lower: $215
MI 15" SS FF Handguard: $200
Precision Armament M11 6.5 Muzzle Brake: $120
Magpul STR: $80
Std Buffer tube, receiver ext. plate, castle nut: $45
JP 308 SCS: $120
Timney 3lb Single Stage: $170
Battleline Ambi Safety, Troy Ambi Mag Catch/Release: $110
DPMS bolt catch & Mag release button, MIAD Grip: $45
BTE Adj Gas Block and gas tube: $50
Takedown and pivot pins: $15
All Detents, Springs, plungers: $15
Total: $2,995
I think he paid somewhere around $65 or so in shipping on top of that. I had a whole bunch of detents, springs, plungers, retainers, receiver ext plates, castle nuts, etc that I ended up using. So it probably came in even lower than $2900...