In my opinion, getting away from the fee for service model is one of the routes we ought to be taking to address healthcare spending in the US (if you're charging per service, you're incentivized to perform as many services as possible in a given encounter).
Contractors, many of whom are small businesses or individuals, do this all the time. They also give estimates like "If we find mold behind the wall, it will be an extra ten thousand".
Medicine is also odd in that you have to pay for the doctors mistake. If the doctor prescribes a less effective drug, it has no effect and then after doing your own research find a better drug and get the doctor to prescribe that instead. You still have to pay for the first visit. If a plumber decides to go from plastic to copper pipe mid job, he doesn't get paid for the work he ripped out.
Multi billion dollar hospital groups, full of highly educated professionals apparently can't pull this off but the guy who poops in a bucket on the job site can.