My therapist is currently working for a company that has huge billing department. One of the reasons she is opening her own practice.

The insurance company pays very discounted rate to what you are billed. Depending on your insurance it's either a set price for each service no matter what is billed, with other insurance it's a percentage.

You should be able to go online with your insurance company and see what is being billed and what they are paying, might be a bit of an eye opener, it was for me.