That $10 dollar fuel filter can't possibly have fixed my engine trouble! It still seems to be running rough to me. I think I really need a new engine.....
But sir, I test drove it and it ran like a champ...
Bah! I'm going to a real mechanic to get a compression test....
Sometimes people just think that expensive = better. The more you charge for something, the more enthusiastic they are about it. The very fact that a piece of wire costs 20X as much as zip cord makes these folks act as if it's automatically better. Their stereo suddenly sounds better and they tell everyone they can to buy the special wire. No amount of explanation will ever get them to believe that lamp cord does the job just as well.
After a while, they are so deep into the special wire story or whatever, that they can't back off the claims because they will look like a fool. They've told all their friends, argued at length, lost a few friends, spent a lot of money, etc...
They now have a stereo system that costs 10 or 20 times as much as their neighbor's, and their neighbor still can't hear the difference.