The exact same thing happened to me a couple of months ago.
I pay over $450 a month in insurance, and thank God, I am healthy—never using it. I was talked into the “free” screening. A “benign tiny polyp was removed” (their words) when I was “out” (wow, that was good stuff...)and my part of the procedure went from my $30 copay to over $1,000. Alas.
apparently, there is a fentanyl shortage...one of the two drugs usually used in scopes...and I was on the short end of the stick so to speak with the inferior drug....