It's a custom device (Score 1)

http://www.youtube.com/watch?v=nb-SlbL_cJg

The device has to be custom fitted, custom calibrated, and hand made for each patient. It needs to fit perfectly in your ear. Custom medical appliances are expensive. You can have a cheap one that doesn't really work, or you can put a horn in your ear like in an old cartoon, or you can pay experts (doctors and engineers and skilled labor) to make the right device to cure your problem. It isn't a scam, or a flaw in the market economy.