Yeah, had a few clients like that
Some, with the CEO being the obstruction.
We simply raised our $135/hour rate to the problem child $185/hour rate and for a special few, $235/hour, and one, $250/hour.
As no other peer would accept their business, yeah, it was worth the effort. With the two highest rate charged companies, I was given free hand and given that no other company would deal with them, it was priceless.
If someone doesn't know or understand, I'm patient and can educate the village idiot, but abusive and obstructive, those are folks that I explain to all listeners about that invaluable individual being a primary example of why one does not poke baby in the fontanelle - repeatedly.