I get the point you made on 250 gb 7200rpm notebook hard drives, this won't happen for a while. but intel has "worked closely" with apple for the past year. Whose to say that intel isn't working secretly with apple?(that's the way apple likes it and it's their tradition). Watch the cnn interview after mwsf with steve jobs. They ask about upcoming products and steve just does his best to avoid answering his question.
So, intel may be the ones developing an apple version of santa rosa to give apple an advantage in the market since they don't yet use any of intel's premium pc platforms/marketing names like: viiv and centrino. Perhaps intel and apple secretly developed an apple version of santa rosa. It's possible, and would be great for macbooks and macbook pros to come with a mac version of santa rosa that would further differentiate macs from pcs considering the two are becoming more alike in parts since the switch to intel. It would be a logical move for apple and intel to co-develop such a new technology exclusively for macs. A new marketing name for the platform could be used and would be a big boost in sales of apple's laptops which would mainly come from switchers because of the new intel technology.
flame me if you will, but its all just a mere opinion, and also could be a possibility.
Apple will probably never take the centrino name, they will only take bits and pieces of the hardware. I'm just saying it would further increase the popularity of apple amongst pc users if intel developed a platform exclusively for macs, steve jobs probably wouldn't object to an intel idea like that. They may not even come with a clever centrino-like marketing name added to the label of an apple notebook. They may just state that intel exclusively developed or they "have been working closely with intel" (like they've said in the past) to create such a product.
All that said, there is a small possibility of an Apple only platform developed for notebooks to further differentiate their products from pcs. (other than the fact that they run os x. I'm talking hardware-wise)
also if intel made an apple-only chipset it would illiminate your high cost predictions, it might just be slightly higher because of the extra work from intel, but not much.