Hmm. And yet, many people who do exactly that end up spending much less for entertainment than they were spending on cable.
My specific example: We dropped an $85/month DirecTV bundle (which had been grandfathered in over several years) in 2008 and went with Hulu+AppleTV+DVDs. Out the gate, we set our budget at $20/month. It was easy to stick to. We've added Amazon Prime (primarily for shipping) since then and changed Hulu to Hulu Plus (and gotten rid of the laptop sitting next to the TV in the mix), but still manage $30/month overall ($40 some months, but that is completely in our own control). This is a family of eight, with kids aged (now) 6 through 17 and the varied programming needs/desires to match.
The main strategy here is simple:
* Hulu is ad-supported and lower-quality streaming. Use it for the "B-tier" shows.
* iTunes is more expensive, but is also higher-quality and can be downloaded and watched anywhere at any time. Use it for "A-tier" shows.
* Past seasons for catch-up can often (but not always) be bought on DVD and ripped cheaper, or just watch them on Hulu/Amazon if available there.
If we want to budget a little less one month, we "skimp" and watch those shows on Hulu (or not at all and catch up later on).
We watch probably 80% of our content on Hulu. The remaining 20% goes to Apple for iTunes shows. This keeps us well under budget for our month-to-month entertainment costs, and still with a very healthy backlog of shows (more shows to watch than we have time to watch them, to be honest!)
The thing is, though, if we went to 100% iTunes (cutting out the Hulu Plus subscription), we still would be less than what that DirecTV subscription would cost us if we subscribed today ($125 was the last estimate based on their current packaging structure; $22/month * 5 is $110/month). At the very least, it is competitive. With our current setup, though, we are in control of how much we spend each month, rather than being locked in by the satellite or cable provider.
What you seemed to be asking for is hulu with iTunes slection, which by the way wouldn't be a la carte. Second the price of the streaming would go up due to many more networks being involved, last they would have to sign a new deal anyway since they don't have any rights to stream in which goes against the whole ideology of your original post of apple all ready having access to all this stuff.