Gam3r01 :
I would call 400 mainstream, 200 is entry level, below 150 is basic.
Entry-level buyers will be able to play any game with a $100-$125 card (of course at lowered settings).
Mainstream buyers might be looking at $150-$200, "enthusiasts" (with money) will probably spend $300-$400, but much over that and you're looking at a smaller and smaller piece of the market.
I think I would re-classify those tiers. To me, entry-level people stick with whatever they bought in their system. For the entry-level consumer, that's probably the built-in graphics from their Intel/AMD CPU. It's probably also the "mainstream" tier.
Next is the tier of those who are willing to upgrade their GPU for more performance, but don't want to pay a large price tag for the absolute best. I might call them the "budget-enthusiast." They know a $100-150 card likely isn't that much of a performance upgrade over what they have, so they look at the $150-300 range.
The "enthusiast/spender" is the one who really wants the performance & is willing to spend to get it. They are the ones who think the cards at < $300 won't cut it for them, and they are willing to spend $300+ on a much higher level of performance. Some are spenders who just want to have the "best" available, even if their game selection doesn't require the best.
Of course, this is just my "executive summary" type of classification. I think the 1070 will fall more into the "enthusiast/spender" at first, but it's getting close enough to the top range of the budget-enthusiast that it will likely tempt quite a few of them to spend "just a little bit more" to get that jump in performance (that's how I would justify it to myself!).