This is kinda the scary part of insurance, and it happens in every industry where insurance exists. It's very expensive for insurance companies to fight charges

This is kinda the scary part of insurance, and it happens in every industry where insurance exists. It's very expensive for insurance companies to fight charges, so generally mechanics know a magic number they can give that is way higher than they'd charge you, but the insurance company wouldn't bother to fight. Ever have work done on a car/boat and have the mechanic offer to pay your deductible? I've had it happen most of the time. And this part of insurance is hard to fix simply because of how valuable people's time is, and the cost of the insurance company simply being wrong in the end (reputation hit, possible legal repercussions, and cost of the investigation).