The lower I've had for quite some time and use with several uppers. The only change to the lower is the VLTOR clubfoot stock at $115. With my M4 upper, I slip the Colt M4 buttpiece on.
The upper w/o scope and mounts or bipod was about $1600-$1700. Some items, like the 600M BUIS came from EE so you may spend more if you duplicate mine,(or less). Of the $1600-$1700, $550-600 was for the OP Inc. 2 port comp and collar and the 2 KAC folding sights.
You can get everything you need from Wes at MSTN. The key to the system is the 18" Compass Lake SPR profile, Douglas SS barrel with matching bolt purchased through Wes for $450. My goal was a Mark 12 Mod 1 so Wes supplied the right KAC gas block, long FF RAS and OPs Inc. 2 port comp and collar along with some of the smaller pieces. He installed the gas block, comp and collar for me. The prices do not include his labor (or mine). I had already collected the receiver, CH, bolt carrier, 600m BUIS, bi-pod, etc. and assembled the rest myself.
YMMV,
Ed