When I go to Starbucks to buy my coffee, I get a beverage that has a certain level of caffeine I like, lots of milk, is sweet and will last me the better part of the morning. I found out that they have a product that I like and it's a repeatable experience: I go, I ask for my favorite brew and it has the same qualities that enjoy, every time.
When I look for an app for my phone, I can see screenshots of it and see the reviews and ratings. Neither of these are very reliable, for reasons I assume I don't need to elaborate here. At this point, I have the two options: 1) I can go online and do further research to try to separate truth from crap; or 2) I can install the app.
When it turns out that the app is crap after all -- or that it's good, but doesn't do what I need, or that it's excellent but the stuff I happen to need doesn't work for my phone or OS version -- I have to uninstall it and look for a better one. Or give up.
At this point, I've "paid" with my time and effort and hopes, so this is where the difference between free and $1 dollar is a lot more important than $1 dollar and $4 or $10 dollars. If the application was free, I feel disappointed and disgruntled. If it wasn't, I also feel ripped off.
But the most important part is that this whole process is repeated for every app. That is where the comparison with Starbucks breaks down: shopping for apps is fundamentally different from buying coffee at Starbucks. The comparison with movies is a lot better, because every movie is different and every movie is a gamble. Then again, movies still have more alternatives than apps: I usually go to see a movie because 1) I'm so excited about it that it doesn't matter that I'm risking a disappointment or 2) I want to spend some time relaxing with my wife and it doesn't matter that much whether the movie was good or decent, as long as it isn't godawful.
Bottom line: when it comes to purchasing apps, the reliability needs to improve. Alternately, I wouldn't mind if every paid app had a time-limited, full-feature free version. Whatever the cure, the problem has nothing to do with the quality of the goddamn coffee beans.