So Marco offers his take: he's been selling an app in the store for $9.99, and it's going just fine. He has tips for how developers can sell their own apps for a higher price, and he settles on some good compromises for everybody: deliver a real value with your app (as economists know, an app is worth what people are wiling to pay for it, so if you produce an app that is worth $10, people will happily spend that much). Respect yourself as a developer, and don't cower to cheapskates (some people won't be happy with anything, even when it's free). And perhaps most importantly: offer a free version.
That last one may be the key -- our own Michael Rose was sold on Instapaper only when he tried it out. More and more, I'm thinking that it was a major mistake on Apple's part not to allow developers to easily offer demos and upgrades in the same app -- people are willing to spend money on an app that's worth it, but not if they aren't sure, and trying it goes a long way to making sure. I'm not in favor of app store developers banding together to raise prices, but Marco is right: if you make an app that's worth $10 and put it on the App Store for $9.99 (with an easy way to demo it out), people will come and buy it.