Ask HN: Does an app need to be big to make money?

I thinking a lot lately about building a web app to start a business. However, if you look around, all companies that are making money in the web business have really big/huge apps (lots of features, too many moving parts) or some sort of physical extension (selling goods, renting places, etc) which increases complexity a lot and has a greater entry cost that is almost prohibitive for someone who works full time and has only a few hours per day to invest in an idea.

So, is there a place for small apps to make money?

Edit: It would be nice if people could post more examples of successful businesses like patio11 did