Re: Best cases of guitar snake oil?
I see something very similar happening in the cable world. Take HDMI cables for example. At most brick and mortar type places I see HDMI cables being advertised for $30, 40, and even higher. I bought mine for $3 shipped online. Why? Because the signal is digital, which means it either works or it doesn't. 1080p is 1080p with a "cheap" cable or an expensive "cable." There is no quality improvement.
What I think is happening with guitars is perceived quality. You spend much much more on a cap or premium tailpieces and expect it to sound better. Therefore it does sound better. It's an effect similar to Barnum's "People want to be fooled" theory.
Granted, I think replacing a plastic nut with one of bone is a good upgrade. Upgrading really bad tuners with something that'll stay in place longer is good. But these boutique upgrades - the caps, tonepros, etc - they're preying on a guitarists obsession with getting the perfect sound.
Also, on the "Gibsons cost more because they're built better..." statement, I think the elitist proved that wrong years ago.