Is any organized collective action from the public possible here? What if we had a service that would take your itemized bill and spit out the fair market pric

Is any organized collective action from the public possible here? What if we had a service that would take your itemized bill and spit out the fair market prices. Then, you would tell the hospital/doctor/insurance that you would pay this price and nothing more. If enough people did that, could it actually work?