That's all true, but from a practical standpoint providers really have no way to accurately estimate a patient's out-of-pocket financial responsibility in advance. The current HIPAA adopted standard transactions don't allow for sending a prospective claim. So all they can realistically do is perform the procedure, submit a claim to the patient's health plan, wait for it to (maybe) be paid, and then send a bill to the patient for the balance.
https://www.cms.gov/priorities/key-initiatives/burden-reduct...
The good news is that CMS is working on an update to those standards which will at least make prospective claims technically possible. Although it may take years until that functionality is widely implemented.
One can always craft some excuse, which is how the terrible system continues to perpetuate itself. Doctors cannot even tell you how much they themselves will charge for anything. The problem I'm describing originates completely with them - no escaping blame here.
(And "might take years" lol. How about eliminate whatever flagrant regulatory capture is allowing providers to create and enforce post-facto and downright fraudulent bills in the first place, and watch the system reform itself overnight)
Nothing stops a doctor or an office from saying "treatment X costs $Y."
Doctors can't say how much an insurance provider will cover or what a patient's out of pocket will therefore be, but that is a separate issue further downstream of clear pricing for treatment.