'''And finally, we tried something else: We made our software better. In late 2002, we released FogBugz 3.0, a vastly improved product at a higher price. The launch was a huge turning point. Our sales, which had been averaging $7,000 a month, shot up to more than $30,000 a month.'''
I'm not making $30k a month (it's more like $30 million), but otherwise my experience has been the same.
This has always been one of my… well, whenever someone asks "Why isn't my app selling?" I find it so very very hard to not blurt out "Maybe it just sucks?". But I don't usually say that unless it's 2am at WWDC or something.
Learn to be your best critic, and you'll learn to ship software that's worth paying for*. If no one is buying your app then you've either got a dud and you need to focus on something else, or you need to improve your app so it's worth paying for. And some apps, no matter how flashy or awesome or genuinely useful, will never make money.
* It amuses me to no end whenever someone tells me how wonderful and crash free VoodooPad or Acorn is. And I'm cracking up inside because they don't know how the sausage is made, and I see the apps crash all the damn time. On the flip side, I want to strangle anyone who says "Oh it crashes all the time", and never send in a single crash report even though I make it super easy to do so.