"Why have reasonable AirPlay peripherals failed to materialize? "
Let me preempt by saying I know that BT is cheaper and better (in many regards), but I like the larger range and central control of AirTunes via iTunes over my network through my two Expresses. But a portable speaker system wont get bellow $200 when you can get a BT set for half that? Is the Apple license and hardware that stupidly expensive or is the physical technology that boutique to remain a niche luxury to audio manufacturers? at this rate (2 years in), it's looking like a slow death or soon only Apple will implement it with their Airports. BT continues to win by strength of numbers and buying power.