I think the discussion about price is too early given that we know nothing about the device still.
But considering the climate for gaming hardware, I don't see it going more than $300. It'll be a hard sell if it goes above that, and especially now that both PS4/XBO are on that price ball park currently, the NX needs to be at a competitive selling price even if it's a new thing because the other devices are still pretty much on their prime.
$299 for a "home console" isn't crazy though, but given how the gaming community judges prices based on processing power nowadays, we'll just have to wait and see.