My last visit to the dermatologist was over $1000 for an office visit that involved a skin tag clip with a scissors and two squirts of LN. Medicare negotiated that down 70% to their preapproved rate and paid about $300, of which I paid 20%. Medicare is just another insurance payer, not a health provider.
If you are talking about the US, we have several times in the past negotiated our bills down as much as 20%. It does not appear to me that there is anything illegal about that.
But it does gall that they try to charge someone without insurance and with no bargaining power the full rate, well knowing it’s a fake rate.