So it seems it's not so important if Zen has same IPC like Skylake or Haswell (or even IB). At least not important for vast majority of PC users. And I'm sure price will be adjusted according to performance
Price always follows performance. The more powerful the chip (in relative terms), the more valuable it is, and therefore more willing people are to buy it.
That's why Intel can charge $1750 for a 6950X and have people buy it. It is the highest-core count desktop CPU out there, it has the highest multithreading performance out of the box, and it can overclock to ~4GHz (if AdamK47's sample is representative).
Anyway, tying this back to Zen, I think Summit Ridge will be priced at a slight discount to its performance. Intel is a much better known brand than AMD, so AMD has to overcome the mindshare deficit by offering greater "bang for the buck" so to speak.
If they have something akin to an 8 core BDW-E in performance, I can't see them offering it for $399, but for, like, $899 -- this undercuts Intel. If they have something more like a 6 core Broadwell-E, then I'd expect them to charge $350.
That being said, the problem that AMD faces is that Intel's margins on these (relatively low volume) parts are so high compared to the rest of their business, they have a lot of flexibility to adjust pricing down to match. And, on top of that, Intel has the brand/mind-share advantage.