Unless NX is a complete hardware revolution so that it is not seen as a direct competitor to PS4 and Xb one, I think a price above $299 will make it very hard for NX to sell well. And even at $299 it could struggle if there isn't a major point of difference.
The problem is, at $299 in 2016 the current PS4 / Xb one tech is probably only moderately profitable. So if NX is more or less a traditional console and they want to sell at a profit or break even from day 1 then the specs will probably not be vastly different from PS4/Xb one. If they want to make a console with specs ahead of PS4/Xb one by as much as Wii U is ahead of PS3/360 then, then I Nintendo will pretty much have to sell NX at a loss.
It also still comes down to software, Is Nintendo going to offer software that grabs the attention of 7th gen PS360 gamers who haven't moved to 8th gen yet? Or will it continue to offer games that largely only appeal to the Nintendo core? Or will there be an attempt to recapture the Wii audience who largely turned away from gaming after they had got their fill with Wii?
I think there is so much unknown about what Nintendo plans to do that pricing is just one factor which may or may not have a significant influence on whether or not NX succeeds like Wii, or NES or SNES, or fails like GC or Wii U.
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