You can buy a subscription for Pandora or Slacker through the app or on the web... but guess what? They are the same price. That's all Apple is requesting, that non iOS app prices are not lower.
Any why would these companies want to charge less than the in app price?
Firstly. They aren't requesting. They are demanding. Secondly margins are very thin for services such as Pandora or Netflix.
So Netflix charges 9.99/month.
If bought through Netflix via the web it's 9.99/month.
If bought via App then its still 9.99/month, but Netflix has to give up 30% to Apple.
Which means Netflix won't be making any profit via the App.
This means that the Netflix app will be pulled from the App Store.
This means the customer loses.