If they push the price too high then Netflix has the money to go directly to the production houses and buy shows themselves. I know they are experimenting with this now, but it is a model that will become more and more attractive.
You bring up a good point about Netflix/Hulu going direct to buy their content. I think we are seeing early signs of this, but it has been taking time to gain traction. Some of the early Hulu exclusives such as "If I Can Dream" were epic failures. But there have been successes as well, such as "The LXD".
The fact that some of Netflix shows failed isn't really relevant - the fact they commssioned them at all is the thing that should have content providers worried.