More than that, I can get an estimate upfront, that in 100% of cases matches the bill unless they find something additional they need to do, which they'll inform me of and create a new total estimate for.

Of note, my vet insurance doesn't negotiate on my behalf; they just pay X% afterwards. The price the provider quotes for a given service is the price everyone gets (probably; some of the smaller vets might modify it if someone is low income and in need).