You're right, patients get an itemized bill. The thing is the bill is pretty cryptic with CPT codes (and modifiers, ICD codes etc) practically unique to each payer as each payer interprets the AMA's guidelines differently. Payer A, say Blue Shield, asks for codes 99453 while Payer B (e.g. Aetna) wants code 92502 for the same procedure. So the patient is really clueless to know if 1) it's the right code, 2) they got charged too much, or 3) the insurance made a mistake in adjudicating the claim.
I know a company that was trying to help patients understand their medical bills, and for one bill, the hospital accidentally put down 10cc for an antidote for a snake bite, 10 times, when it should have been just once. The cost was in the tens of thousands instead of the thousands, and the hospital eventually fixed the claim and resubmitted, but the insurance company simply billed the patient.
I know a company that was trying to help patients understand their medical bills, and for one bill, the hospital accidentally put down 10cc for an antidote for a snake bite, 10 times, when it should have been just once. The cost was in the tens of thousands instead of the thousands, and the hospital eventually fixed the claim and resubmitted, but the insurance company simply billed the patient.