So what you guys are saying is that the MBA is a second-tier laptop, while the rMBP is the premium offering? After all, they are both thin and light, but the rMBP is more powerful and has a higher screen resolution than the MBA - for a higher price. That makes the MBA a lesser laptop than the rMBP, and that justifies the price difference.
You got it. Exactly. The "pro" really is Apples premium laptop. Although the rMBP 13" really needs a spec bumb soon to justify the price.
But yeah. Apple has always had to linies - for consumers (iBook, Macbook, Air) and pro (Powerbook, Pro, Retina).
Air needs to stay below the retina, so Apple can charge a premium for their retina.
"Lesser laptop" is not really possible - either it's a laptop or not
I had to pay 500 $ in difference from a upgraded Air to rMBP13", and I'm a student who uses CS and Office a lot, and that difference didn't justify the display for me, so I didn't bought it. The MBA also uses turbo boost cpu's which makes it close to the rMBP13". Retina 15" is another story (and much more powerfull). So if you got the dough and want a nice display then go for the rMBP 13. But keep in mind that 1 revs is a dangerous game (see the numerous threads on IR, lag and whatnot). I'll plunge for retina once it's tested and might be in the all laptop-line in 2-3 years.
I'm not neglecting the "niceness" of rMBP13, I'm just poor and can't afford to pay a premium price for a not premium-spec'd laptop.
The 500$ saved could be used on a iPad Mini, external display, iPhone and so on.