Would you accept a locked-down device that offers a cheaper product, or is it 100% about the principle? For example, armed with the knowledge that Amazon can pretty much delete any book they want from your device at their whim, is there a price low enough that you'd be willing to pay? $1 / book, $20 for the device itself, for example.
Sure we all have our price. For the device if it is a locked down single purpose device I can't see paying more than the cost of the actual plastic and silicon it's made from plus maybe 10% for profit after all they did develop this wonderful device. For something open I'm willing to be more reasonable and I'll pay what would be expected, with the exception of if you are charging me 100% markup above materials, but that's not really reasonable anyway.
For media that I cannot control I would be willing to pay up to and no more than absolutely nothing. If I paid for it and you can take it away, I may as well not have paid for it because I sure as hell will NOT pay for it again. Give me a product that I can control and use the way I want to and I'm willing to pay a fair price for it whatever that may be $0.75/song $15-$20/book etc.