You're presuming without evidence that an Air in 2005 or so would
not be successful. Moreover, it need not be an Air as we know it, but simply a MacBook with no optical drive and a 10-11" screen. The tiny Vaios of the time did fairly well, and with healthy margins.
I'll stipulate that I have no clue what BTO infrastructure costs.
However, I do take umbrage with the notion that power users will simply see the light one day. Most of the time, it's not a matter of preferences or delicate sensibilities, but needing a tool to do a job. It is today impossible to have a modern Mac laptop with five extra batteries, harming a certain user segment's ability to work while traveling. Soon, it may be impossible to get a modern Mac laptop with over 512G of storage, which sucks for someone, say, editing video in the field. (Dangling an external HD sucks; you're one jostled cable away from serious data loss.)
I have no issue with the "applianceification" of computing; in fact, I'm all for it. But because this has been Apple's focus, they've spent less effort in recent years on professionals for whom Macs are vital tools (see also the Final Cut fiasco). Maybe those users simply aren't profitable, which would be very sad indeed, given the alternatives.
Hopefully, cheap and huge