Something's fishy with my dentist... 🤨

I’m trying to figure out what the going rate is for a white filling these days.
Also, does having supplemental insurance actually cover any of this, or am I still on the hook?
My dentist is asking me for $33 for a molar on my right side, 😕
but here’s the kicker: about a year and a half ago, I already paid full price to get a filling on that exact same tooth. $10 If I remember correctly, the old filling just gave out, and now she’s insisting $33 that I pay again next time.
To make matters worse, if I ask for a formal receipt, they just hand over those standard payment slips you see everywhere—the kind
where you can basically buy a slip at a gas station or a CVS and just pay yourself. It’s a joke, really. 🙂
On top of that, I’ve heard stories about dentists just making up their own prices on the fly. $33
Some places charge $50, others want $70, $30 depending entirely on whatever mood they're in.
Some don't charge extra at all, while others seem to pull numbers out of thin air. What am I supposed to do here? How am I even supposed to confront my dentist about this? Thanks!

Not suspicious, just being cautious😛

I have supplemental insurance, so I don't end up paying anything out of pocket. But I did hear some people have to pay a co-pay for fillings $33. You should check with Medicare