Those cheap things are not 'hearing aids', they're 'hearing amplifiers', which is why they are cheap (I wear hearing aids, and I did try a hearing amp once to see what it was like; I returned them). Real hearing aids are totally adjustable by a trained audiologist, who can work out the best EQ curve for you, along with multiple settings for different EQ's. Those cheap ones can be of some value, but they are far, far inferior to real hearing aids, hence far, far cheaper.
