How much for a Skylake-based system? Very rough and ready component selection from MSY and PC Case Gear.

CPU	i5 6600 (modest)	325
CPU	i7 6700K (one-off cost for ongoing performance)	519
Mobo	Asus H170-PLUS	169 (H170 PRO GAMING would be a solid choice too, at $230)
RAM	16gb of DDR4 2400MHz or whatever	150
SSD	Samsung 850 EVO M.2 120G/250G/500G	99 / 135 / 243
Case	Antec P280	169
PSU	whatever	100
OS	Windows 10	???

If you want to cheap out a bit, you can tweak a few little things:

Select a basic H170-based motherboard: Gigabyte or ASrock will be somewhat cheaper, but it still bottoms out around $150. The cheap Asus H170 board is $160 and it uses DDR3 RAM (widespread, cheap, will become "old" in ~2yrs)
Use DDR3 RAM: it's cheaper and still very performant, just not future-proof. You can get 16gb of DDR3 for $115 at MSY, but will need to buy a mobo that takes it
Use slower RAM: Baseline DDR4 RAM is 2133MHz speed, very slightly cheaper at about $140 from MSY
SSD: you can cheap out a bit with a different brand SSD and maybe save $20
Case: the P280 is a fancy noise-dampened case. You can pick a basic one and maybe halve the cost

Choice of CPU

Current socket is LGA-1151.

April 2016

CPU	i7-6700K	484
Mobo	Asus H170M-PLUS	165 (H170 PRO GAMING would be a solid choice too, at $214)
RAM	16gb of DDR4 2133MHz or whatever, eg. Corsair Vengeance LPX 2x8gb kit	112
SSD	Samsung 950 Pro M.2 256G	265
Case	Fractal Design Define R5	145
PSU	Corsair RMx something	150
OS	Windows 10 Home/Pro	137/199

Using my existing GPU, that's a total of 1458 for the cheaper choices, and 1569 for the expensive ones (Windows Pro and Gaming mobo).