It's the old placebo effect. If you believe a pill, or tonic, or armband will make you feel better, then it will make you feel better, psychologically. If you feel better psychologically, you will start feeling better physically, too: you'll feel you have more energy and stamina and strength.
If so, what's the problem? If it works, why question it? 1.) So long as people aren't aware this is what's going on it leaves them vulnerable to being financially exploited ($300.00 sunglasses?!?!) and 2.)there is always the risk they'll find out they've been had, which will just send them into depression, reversing any good effects it's had.
Better to get your feelings of well being from things that are authentically beneficial: good nutrition, exercise, all that stuff.