Medical service as rent extraction? Sure, whenever a human need is turned into hostage taking. One advantage of public government as an exclusive (or dominant) rentier is that its price is set (by reasonable governments) closer to actual costs rather than the rip value. Which actually can facilitate service exchange better than the free markets as we know them.
They talked about a medical clinic, built and operated by cosa nostra, where everything cost five times the "real" price (i.e. when it finally got cleaned up, they reduced costs five times with no lowering of the quality).
This is both an exact illustration of rent extraction in itself, and an interesting parable of private medical care in general. It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II