The $99/year is mostly just away to filter out some of the noise from their review queue and tech support I think. I don't think the revenue from it matters at all to apple.(i'm sure if they thought they could get more quality apps by dropping the subscription, they would. You can still dabble with iOS development without the subscription.
I don't mind paying -some- price and I gladly fork over money for a good product or service. I bought Coda for $99, and MarsEdit for ~$40 and countless other great software.
However, paying $99 for the right just to develop against an API so I can add it as an option for an app I'm making doesn't compute for me.
I'd probably not use the service enough as a regular user to warrant it either.
