How far would the rates need to be raised for you to be interested? The reasoning behind my current price structure is that I often find myself aimlessly wandering the app store and eventually download a few free apps and usually get suckered into a paid app. My site (assuming it grows) would provide a way to aimlessly get exposure to apps and either get paid a small sum for trying out a free app, or get a paid app for free.
All in all though I think your idea of MTurk has merits and will certainly be checking into this option.