If you think an App isn't worth the price asked for it, don't buy it. To steal it means you don't care if the developer can earn a living, feed his children, and keep a roof over his family's head. It's like someone coming up to you, after you get your paycheck/allowance, and taking it away because they don't feel you earned it either.
If you like an app, support the developer so they make more apps you like.