I don't understand. Robust markets don't have large margins. Why would a regulator even want markets with enormous margin? That's usually market failure.
Most people also complain about how pharmaceuticals are greedy corporations that seek to exploit monopoly status for profits above human health. Hardly a good example of a well functioning market.
Complaining doesn’t mean action. To affect prices people need to vote with their wallet, and they won’t do that when their life is on the line.