People are willing to pay half a million for tiger bones in order to cure "diseases". You can't go around selling tiger bones for $2, they would obliviously not work.
Same thing for glasses. Same thing for walking canes.
Point taken, though the effectiveness of glasses is (I would hope) a little less likely to be the product of placebo effect. The high prices of glasses feels more like a matter of branding and style, in the same way a t-shirt with a swoosh on it costs $30, and one without costs $10 (USD).
