I don’t need every customer. I’m primarily in the business of selling a product for money. How much effort do I really want to devote to satisfying people who are unable or extremely unlikely to pay for anything?...
Maybe you think there aren’t enough people willing to pay $5 for an app with no free version. I used to think that, too. But I was wrong.
I’ve made a lot of assumptions in the app market over the last three years that turned out to be wrong. Most frequently, I underestimate demand, both for my product and for others.
Marco Arment in “Why Instapaper Free is taking an extended vacation”