Much like sports cars, computers get more expensive when they get lighter. I don't actually know if Air is lighter per se, but it is thinner thanks to the laminated screen.

I think it is kind of similar for macbooks now, if there is a suffix, it means it is somehow better than the base model. (although macbook Air is larger than a macbook... which is weird)

I honestly only know that the pro is more powerful. I don't get the rest of the lineup. I don't get why the new air isn't a macbook (or vice versa) for example. They seem to occupy the same space. Added to that, imo, the macbook is the best industrial design of any laptop ever released and the air wedge shape the worst recent mac's but they decided to revive it for some reason. They should have just made a bigger macbook. Their product line up is a disjointed mess.

I too think that on macs the air should be macbook and vice versa. However then it runs into the issue that classic macbooks have really slow processors whereas the air is faster. At least on the iPad side the Air comes only with benefits.