I don't really blame them for getting duped, because unscrupulous companies are trying to dupe them.
Being that I own one of those companies, I thought I would chime in on this topic.
For starters- our Tube Screamer derivative is called the Dead Horse- I think its probably easy to figure out why. Additionally- We tell everyone right up front what it is. Its a hyper modified TS. But people like the mods that we've done. We've had other overdrive designs, that were not based on the TS, but simply said, they didn't sell, so we ended them.
Why do people buy boutique TS clones rather than a cheaper pedal? People buy them because they're built by hand with better components than the original, and/or modern day knock offs.
Why do people at TGP buy so many? Because each boutique manufacturer puts their spin on it. Example: My company markets to the metal crowd... so we extended the gain range, added more bass, and leveled out the mid-hump.
Some boutique guys like the exact opposite, so that's what they'll sell... and this continues on and on- a tweak here, and adjustment there- the little changes can make a huge difference.
I hope this sheds a little light on the thought processes involved.
Best,
Dennis