Well not Nvidia/AMD themselves, but AIBs that sell the cards. Like for example the Asus DirectCU Mini.
I don't believe they've used that on any top of the line chipsets, though, have they? I know they have a 970 version, but no 980 or 980ti.
More pertinently, though, the economics are different when it's AMD producing a dedicated "Nano" card versus Asus taking an existing card and putting a smaller cooler on it. For one, Asus are using the exact same 970 chips, whether they're going into one of their DirectCU Mini cards or one with a full-size cooler, so the prices will naturally be similar. AMD, on the other hand, have the benefit of being able to bin their dies, so hypothetically the best performing ones (i.e. capable of hitting the highest clock-speeds) go into the Fury X, and the lowest performing ones are capped at lower clock speeds in the Fury Nano. The lower-binned dies are cheaper (or more accurately worth less), which could hypothetically allow them to sell the Nano at a lower price.
Of course, the opposite could also be true. AMD could take the best performing dies for the Nano variant, due to their ability to hit the same speeds at lower clock rates, producing a lower-power card with the same performance as the Fury X. In such as case, you would actually expect the Nano to be their most expensive card, similarly to how Intel's low-voltage laptop CPUs cost noticeably more than desktop variants based on the same die.
Aside from costs of production, there's also the question of how AMD sees the card from a strategic standpoint. They may see it as a good chance to claw back some market share from nVidia, and hence sell it at a lower margin in exchange for those perceived gains. On the other hand, they could see it as you say, as a niche of a niche, and simply try to make a good margin on a card they feel won't have a huge audience.
The issue here is that we have no solid info on performance, no knowledge of AMD's Fiji binning process (if any), no idea of AMD's strategic goals for the card, and no prior history of similar cards to base our assumptions on. It's extremely difficult to make educated estimates of price without any of those things.
