First thing I want to say it that I wholeheartedly support original Arduino products. However, once you start building projects, you realize that a $20 Arduino board for a simple auto-light switch or a plant monitoring system is not worth it.
What I do is I buy a lot of cheap Arduinos in bulk and leave them hooked to my projects around the house. Even if I goof up and fry a Duino (which I do all the time), I don't have to worry about it.
Most of them range from $3 to $5 each. In the video, I review a $3 Arduino UNO, and a $20 Arduino UNO kit. If you are contemplating buying some, you should definitely check the video out.