This might be self justification but I just bought a 1080 for 450 brand new. OCing the 1070 to keep up with the 1080 doesn't take in the fact you can OC the 1080 also. I'm not denying the 1070 is almost as fast but, it's just that.....almost. Plus with 1080s at 450 I don't know why you would want a 1070ti.........unless for mining.
Keep in mind when the 1070 launched it was for around $400 vs the 1080 sitting at $600-700.
Now yeah the prices are still kinda fucked with the NVIDIA cards all priced near each other.
Cheapest 1070 is around $390
Cheapest 1080 is around $490
Cheapest 1080 Ti is around $715
when the price difference was $200 the 1070 made sense you could OC it and get 1080 stock performance for a whole lot less. Now with the prices being so close the extra 20% in terms of money spent directly gives a buyer 20%+ more performance when OC is taken into account.
Previous the 1070 was the better buy now that situation has reversed. 1070 Ti will likely split the difference. What everyone forget is GPU VRAM saw a price hike due to shortages. My guess is GDDR5 is far cheaper than GDDR5x so NVIDIA and its 1070Ti are basically just 1080 core with 1070 memory. To make a cheaper GPU which then undercuts the Vega 56 and Vega 64 by offering performance in the middle while being far cheaper to produce.