I recently built a 2016 S works Tarmac with Sram force etap, for under 4k. I did have to replace the disk calipers with red post mount calipers, due to the frame being post mount rather than flat mount. I recycled a few parts, saddle, handle bars, seat post.
Also, upgrading my 2011, S works Contador tribute Tarmac to Red 22, 11 speed etap. Itll still be rim brakes, but electronic shifting. The wireless ness is awesome.