I can't understand why Apple is calling a non-expandable, no disc drive machine a "Pro" machine.
"Pro's", aka Professionals, do NOT want external expansion boxes cluttering their desk just because Apple deems it necessary to not allow people to expand it's internal components. ("expansion is external")
Professional users also want to burn media (videos, photos, etc) to DVDs and Blu Rays. Now, on top of a ~$3000+ machine, they have to purchase an additional external drive just to do that. Apple is not gonna undercut the price of the high end ridiculously priced 15" rMBP. ($2799)
Don't get me started on the internal storage. WHY can Pros NOT expand the internal storage? Yes, there are external drives, but when it comes down to it, it's yet ANOTHER external expansion box, cluttering an already cluttered desk.