Not mysterious just want you to dig into the deeper meaning of average cost per claim
This is like led of the rings
1 ring rules them all.
When you understand this on your own you will then understand how TOA can do it.
If I tell you the answer you still won't understand the concept of TPA operation

Think about it if you where a glass company doing glass replacements for the exact same discount off list and labor.
What is the one thing you can do to keep YOUR average ticket lower than the. Next guy.

Bentpan,
I think you have it all wrong. I think an average invoice amount is predetermined by the TPA and the insurance company based on actual experience. I think the insurance company and the TPA determine a percent off NAGS and low repair rates that will statistically come in under the predetermined GAI. Then the TPA can make sure non-financially affiliated shops do their jobs at the correct percent off NAGS and at low repair rates so they can manipulate their own invoices to make more $$ but still stay close to the GAI.

JB,
Heres a theory, think in terms of a wholesaler who offers you an average ticket price for the w/s you install. a wholesaler comes to you and says if you purchase all your windshields from me this year, we will sit down at the end of the year and evaluate our average the price. At the end of the year we find you have over paid for the purchases you made measured against the average. You get a kick back.

insurers in order to limit their liability purchase insurance from other insurers in hopes of reducing their exposure to acceptable limits. If the insurer experiences a loss, past that limit, the reinsurance kicks in to pay the remainder of the claim. Think of Lloyd's of London.

A certain TPA/Wholesaler is actually selling reinsurance without actually being in the business of insurance. Selling insurance without a license, might be the term. The TPA/Wholesaler reduces their exposure with network shops payment rates, clearly the TPA/Wholesaler isn't being paid the same amount as the contract signing shop. Signatories are simply adding to the available TPA/Wholesaler funds to cover the kick back at the end of the year. The key is the self sacrificing signatories. Is that close bedpan?