Wasting...you know without water cooling the expensive system would have probably been limited to performance roughly equal to the $1500 system right?
Well yes, most of the extra money spent doesn't really help benchmarks, do they? Same processor and ram.
Blu-Ray +170 - no effect on benchmark
Case +90 - just a case no effect on benchmarks. maybe slightly better cooling??
SSD + 402 - little effect on benchmarks I think, at least not FPS but will affect load times.
That's 660 right there with little effect on benchmarks.
Then
Motherboard +190 - Maybe better overclocks, and extras like USB3.0 etc but big effect on performance?
PSU + 110 - once you meet the minimum power, performance is flat, but extra headway allows higher overclock. Can we have made do with less?
So we're up to 960 with the balance really on the GPU and watercooling.
+190 on the water cooling to allow higher overclocks is probably one of the better bang for buck with regard to the benchmarks.
To summarise, 1500 does seem to be the sweet spot. But you can't look at benchmarks only, the other extras have some value (albeit maybe not 1500 worth)