It's tough to say. Apple launched the AirPods with a surprisingly low price. Since then, the competition has barely been able to match their price and quality.
Looking at the direct competition: Sony's ANC earbuds are $230. Bose's non-ANC earbuds are $200, but the ANC ones will surely be closer to $300. Amazon's new earbuds, with "Bose noise-reduction" will be only $130.
The rumor is they will cost $160-$200, depending on wireless charging. That would be in-line with Apple's aggressive pricing for the AirPods. I think Apple could get away with $250.
$250-300 is too steep. First, psychologically I'm thinking in terms of grands at that point - that's a quarter to a third of a grand. Second, at those prices people will expect ANC to be on-par with the Beats Solo Pro, which it can't possibly be.