Well, based on the speculation and AMD powerpoints(that I have seen on this forum) I have seen, I'd think that the best bulldozer should average out to be about the same as a 2600k or just a little better, and I don't think that AMD is going to try to charge a premium over intel's offerings, as they need some sort of advantage to lure people to their side. That said, I also don't think that AMD will heavily undercut the 2600k because well, 300$ for pretty much the top performing desktop CPU out there is nothing short of a steal. There just isn't a lot of room pricing, really.
So, at best I think we're looking at 200$ of flexibility here, and I don't honestly think that AMD will price any bulldozer core at 100$... That's phenom/athlon territory.