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Will you elaborate?

He's mad that an Arduino + Motion sensor + MP3 player costs $100 when the parts used to make those three things cost significantly less, and the expensive parts are unnecessary to solve the same problem. (The microcontroller on an Arduino is like $1 in quantity. The special terminals, though, are about $5. This is, incidentally, why cheap dev boards like the STM32F4DISCOVERY have more features and are half the cost of an Arduino: they cut out the expensive parts.)

What he doesn't understand is that the economics are different when you are making one unit versus 100,000 units. (But if you are thinking 5 or 10 units, then it starts to become financially advantageous to start avoiding the hobbyist stuff and make your own boards.)

I think the "sonar sensor" is the most egregious, such a thing it $1 in parts but is retailed at $25. That is just ridiculous. The obvious solution was to use a Raspberry Pi instead, it might even be able to emulate the sonar ranging algorithm on the CPU.

I think you can get one of those sonar sensors for $6 on amazon. They're cheap. I don't think the obvious solution is to use a general purpose computing machine...

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