Not all the slides are here, only a couple actually, but Yukon aimed at 299$:Well, you know their original price target was XB1 with Kinect for $399.
http://www.pcmag.com/article2/0,2817,2405922,00.asp
At the beginning of the article.
I don't remember but those slides were quite dated, 2010 I assume as the "road ahead" starts in 2011 (some more slides are here)? It showcases the problem pretty well: inflexible decision process, once some basis decision are taken there is no turning back even if the plan is drastically altered: price and specs.
Going through those slides again I found a 4-6 increase in perf in game, x6 "system wise" which is definitely in line with the way I read the prospective specs for the system.
I think BC and IBM process/edram might have been given upon either fall 2010 early 2011.