This does exist for many areas. Here is the price list for the Hollywood Urgent Care near me:
http://hollywoodurgentcare.snappages.com/services.htm
Note that even fixing a knife wound there tops out at $350.
Under ACA in California, my copay for an urgent care clinic would be $120, per Covered California. A regular visit only costs $69 though, so insurance would cover nothing, unless it was approximately knife wound level.
Real healthcare reform would have included Financial Aid help for doctors and more urgent care clinics.