It doesn't matter that 5820K is cheap because the entry cost for the enthusiast platform is about the same owing to DDR4 prices, I payed more for mobo and about the same for RAM and in the end I ended up paying about the same I would have payed for IVY-E at launch with a 4930K CPU.
1. You chose to buy the most expensive X99 board while $225-250 MSI X99 SLI, Asrock Extreme 4 and Gigabyte UD4 would overclock exactly the same for 5820K and are all sufficient to run Tri-SLI.
2. You chose to buy 16GB of DDR4 but 8GB is fine for every single game on the PC. Unless someone is running photoshop or some video/visual editing software 16GB of RAM is a waste on the PC for gaming.
3. I was making a general point about how cheap owning near flagship CPUs is today. A $300 Q6600 / 6700 @ 3.4 Ghz didn't last 5 years. Core i7 920 @ 4-4.2Gh easily did. Nowadays an overclocked CPU like 5820K lasts 5 years easily without any need to upgrade for most gamers. Most people today wouldn't say that a 4.5-4.6Ghz 2500/2600K is too slow for flagship gaming but those are 4 year old CPUs! Based on how things are moving even these old workhorses can last another 2-3 years.
There has never been a time in history of CPUs where it was so cheap to own near flagship hardware like the 5820K @ 4.2-4.4ghz. I used to love the CPU forums much more than GPU but starting with i7 920/860 @ 4.0 -> 2600K @ 4.8Ghz I saw that for games the excitement for CPU upgrades is dead. Not only were there more CPU limited games in the past but GPUs doubled in speed every 2 years like clock work. That meant your Athlon XP/Pentium 4/Core 2 Duo would become obsolete quickly. Nowadays it takes 3 years for GPUs to double in speed, which basically means the first 3 years of that i7's life it's not even trying and next 3 is only when it starts to be taken advantage of. Unless game development changes, a 5820K @ 4.3Ghz will be good for all flagship GPUs for the next 5-6 years. People will just upgrade because it's fun.
We've even seen BFG test a lot of games and a 4790K only beat 2500K by < 7%. That's horrible for state of software progress OR excellent from a point of view that upgrading the CPU every 2-3 years for gaming now is just a waste of $.
As gamers start upgrading to 4K for gaming, most gaming PCs will become GPU limited. For the next 5+ years the most exciting progress on the PC will happen in graphics and 4K monitors unless some of the SSD makers step up their PCIe SSD game. As far as motherboards, PSU, CPUs, those markets pretty much stagnated. Now when building a PC one only needs to buy an i7 4790K or 5820K, overclock both, get Crucial or Samsung SSD, any good Gold or Platinum PSU and you only have to read on monitor and GPU advancements on the PC. As far as performance and real world changing progress goes for games, the importance of CPU upgrades is finished. Unless Witcher 3 or the next BF game uses 6 full cores, it will be another 12-18 months wait until some other next gen game hopefully ups the CPU demands (granted in an efficient way not Blizzard dual-core threaded engines).
Therefore even of BW-E brings a 10% IPC increase or Skylake brings 15%, it's pointless for gamers unless these 14nm CPUs can also overclock way better (ie, 5.5Ghz on air). Even with IPC increases from SB to HW, the performance increase in games overall is just not there unless you are a competitive ARMA3 or BF4 player where you need every single frame you can get. Where Intel now has to make greater strides are power consumption and battery life in laptops, as well as working together with manufacurers to make super fast PCIe storage, like in MacPro laptops, standard. Most of us will upgrade to BW-E or Skylake because it's fun to play with new hardware. As far as performance increase in games goes, I doubt even a 5Ghz Skylake-K will do much vs. 2600K @ 4.5Ghz/5820K @ 4.3Ghz for 4K gaming with triple GM-200s.