Indeed, if I were short of money and would not like to go deeply in debt but needed to have an Apple's laptop I'd definitely go for the 11" air. It can get any job done within reason. If your budget is so tight that that you cannot afford an Apple laptop you should look elsewhere.
There used to be times when the MBA was significantly lighter than the other laptops on the market. Back then, its thinness and lightness were a distinctive feature and a main selling point of the computer. However, this is not the case any more because the MBP has become thinner and lighter, too. Now a days the MBA is just a slower laptop with lesser features. That's why it's less expensive than the MBP.
Since the price of the retina MBP is getting closer to the price of the MBA (Apple actually offers a 13" rMBP which is just $100 more expensive than the base 13" MBA) we are likely to expect next year the MBA, in its current format, will disappear. There's quite the likelihood that we will have a thinner 12" rMBP next year which will replace the MBA. The future is retina displays and SSDs.
I really hope that they don't have a Retina air since I just purchased a 2013 air to use in conjunction with my early 2008 MBP which is having battery issues.
It was already a hard decision deciding between the MBA or the 13" MBP.
Still having doubts if I made the right decision or not.