Help determining if wrong billing codes were used / overcharged [UC San Diego Health]

I have a Blue Cross Blue Shield Of Illinois PPO insurance plan through my employer. I'm in the state of California and went in to UC San Diego Health.

I got a "COMPLETE PULMONARY FUNCTION TEST" to test for asthma. I read these normally cost 500-$1500, tops….it was a (less than) 30 minute test administered by a single nurse.

Fast forward, total bill is $3,637! Insurance covered 80%, which still left me on the hook for 20%.
The broke the bill down into 3x separate procedure charges "Measurement Of Lung Diffusing Capacity", "Measurement And Graphic Recording Of Total And Timed Exhaled Air Capacity", and"Determination Of Lung Volumes Using Plethysmography".

I looked up the "master price list" for UCSD health [https://health.ucsd.edu/insurance-billing/standard-charges/] and "956006144_UC San Diego_Standardcharges.JSON" [http://hsfiles.ucsd.edu/patientBilling/UC-San-Diego-Standard-Charges-956006144.json].

First, most json readers I tried didn't actually work with the file (format issue), but just scanning through the text (massive 500MB file or something that had to be opened in notepad++) I was able to find the specific names for the said charges.

Within the list, I found the following (note: I have Blue Cross Blue Shield of Illinois, so would fall in the out of state category)

"Measurement Of Lung Diffusing Capacity"

"RecordID": 32553

"Concat_json": "{\"PROCEDURE\":\"2823\"

\"BLUE SHIELD OUT OF STATE BC/BS; BLUE SHIELD PPO\":\"734.45\" <– price that I'm thinking should have been charged to insurance

non-contracted price listed in master charge list: $1177 <– what was charged to insurance

Delta: $422.55

____________________________________________________________________________

"Measurement And Graphic Recording Of Total And Timed Exhaled Air Capacity"

"RecordID": 32533

"Concat_json": "{\"PROCEDURE\":\"2803\"

\"BLUE SHIELD OUT OF STATE BC/BS; BLUE SHIELD PPO\":\"627.74\" <–price that I'm thinking should have been charged to insurance

non-contracted price listed in master charge list: $1006 <– what was charge to insurance

Delta: $378.26

__________________________________________________________________________

"Determination Of Lung Volumes Using Plethysmography"

"RecordID": 32550

"Concat_json": "{\"PROCEDURE\":\"2820\"

\"BLUE SHIELD OUT OF STATE BC/BS; BLUE SHIELD PPO\":\"907.3\" <– price that I'm thinking should have been charged to insurance

non-contracted price listed in master charge list: $1454 <– what was charged to insurance.

delta: $546.70

Total overcharge of insurance: $1,367.51

Total overcharge of patient due to this: 0.2*1367.51 = $273.50

_____________________________________________________________________

I want to fight this merely on the fact that I'm thinking wrong on principle.

I emailed my insurance company, and to quote them they said:

"The claim did apply in-network benefits". …. "The claim was processed correctly per the terms of your plan based on how the provider billed".
"We have no control over the amount a provider chooses to bill for a service. PPO providers have an agreement with us to accept a specified amount for the services they render per the terms of their contract. Amounts in excess of this allowance are written off by the provider and the discount is passed along to you as our member. When you receive services from a PPO provider, you will receive the highest possible level of benefit for services and the provider cannot bill you for the amount over the allowance for the service billed.
Billing and collection of payment is the responsibility of the provider. You will need to speak with the provider regarding the amount the provider has chosen to bill for the services you received. "