I think you and I will have to agree to disagree on this point. I do not consider $380-450 videocards a mainstream market segment. At first, the hype that you can get a $380-450 videocard with Titan X performance will sound amazing, but then you realize for 1080p 60Hz gaming, a $200 card with ~ R9 390 level of performance is fast enough, so why spend the extra $?
Despite how popular 970/980 were on online forums, 970 managed to garner 5.10% on Steam in 1.5 years, while 980 and 980Ti sit at less than 1% each. 970 seems to be the exception, not the rule since the most popular cards are all in the sub-$300 price ranges per Steam:
http://store.steampowered.com/hwsurvey
For example, here in Canada if 1070 reference is $449, it'll show up as $449 x 1.30 = $584 + 13% tax = $660 CAD.
You think mainstream buyers spend that kind of $ on a videocard?
10%? They can be 25-30% slower and still have way better price/performance.
$299 = 100% base
$449 = 51% more expensive for 25-30% more performance is still worse value
$150 is still a lot of $ to spend. It's like going from an i3-6100 to almost an i7-6700! Someone building a new rig would be stupid as hell to get an i3-6100 + 1070 over an i5-6600K OC / i7 6700 + Polaris 10 for 1080p gaming.
The vast majority of PC gamers are also reluctant to admit that older CPUs are a severe bottleneck for 1080p with 980Ti level of GPU performance.