There actually isn't.
http://www.gamersnexus.net/hwreviews/2830-nvidia-gtx-1080-ti-fe-review-and-game-benchmarks/page-6
As for the “Founders Edition” card specifically, it’s still a reference model. Its name sounds fancier and its design looks better, but the thing doesn’t cool well for the GPU core. FET cooling is impressive and competitive, to be fair, but the core is where we encounter limitations on clock-rate as imposed by thermals. This is part of why we couldn’t replicate nVidia’s boasted 2038MHz boost with <80C thermals – you’d need a screaming loud fan to do that, and we don’t consider that usable. That’s potentially misleading marketing and isn’t new to a Pascal launch, with the GTX 1080 being similarly demonstrated during last year’s Epic Games demo. We also had trouble to replicate those findings under usable conditions.
OK so when we take that information and look around? I've seen people on OCUK saying that they upgraded from a 1080 that overclocked very well and at 1440p are only geting 10-15% more out of the TI.
So as I said all along (well, it was pretty obvious really tbh) the 1080ti needs water of some sort. If you want to extract the real 20-30% you need water. And an AIO will void your warranty (as will real water cooling) and you can expect to add at least another £100 to that in the best scenario (an AIO unit or a block for your existing loop).
So that £700 is now £800. That is nearly double what the 1080 costs and it's only 25-30% faster at best at 4k only.
So that's not really a gaping hole. I mean it is in price terms.. Some one (I think it was Paul of Paul's hardware) recently pointed out that bang for buck the 1080 is the far better deal per FPS and it was pretty pointless going from a 1080 to a TI any way, because it's just wasted power.
If you were coming from a 980ti it was far better, but tbh? if people have not upgraded from their 980ti to a 1080 there would be good reason for that. From what I have seen? all of the people buying 1080tis are Nvidia fans, and every one I have seen apart from one on here (that dude who bought it for his missus) has gone from a 1080 to the TI.
Which is just proof beyond doubt that they will buy whatever it is Nvidia are selling. The higher you make the price the less people you will have who will actually pay it. So Nvidia are doing it the short and quick way. Charge top dollar, sell up, move on. Instead of doing what AMD are with the 400 series and selling more for smaller profits.
I have a Titan X and tbh? I've not had a single twitch toward buying a 1080ti. Not a single one. I'm just not paying those prices.