I agree but the amount that is billed to your insurance company is not what they will pay.
Example: Your ins co is billed for $12,000. Out of that they allowed $3,000 and applied $3,000 towards your deductible. You would only be responsible for $3,000. Taking a $9,000 write-off is not unusual.
It really depends on the insurance in question, your policy and if they are in or out of network with that provider or providers.