Two anecdotes in support of your last sentence: I once paid cash up front for a procedure, charged at 25% of the insurance rate. This was put in writing as the

Two anecdotes in support of your last sentence: I once paid cash up front for a procedure, charged at 25% of the insurance rate. This was put in writing as the total cost of the procedure. Afterwards, they billed me as if I owed 75% of the other rate, with threats of legal action accompanying invoices. I did not immediately locate in my files my copy of the initial contract. Like you, I was freaking out. Even after finding my copy, and knowing that I would prevail in court if it came to it, I worried about all the indirect ways the situation could harm me. Eventually they dropped the issue. A friend agreed to a few procedures without knowing the price, and was then charged a bizarre, absurd amount of money (I comparison researched, after the fact). He offered to pay 50%, and they gladly, eagerly accepted. I heard the call, they sounded surprised and happy. Clearly he could have paid much less.