Why don’t streaming services like Hulu or Netflix go bankrupt? After all, most businesses couldn’t survive if customers paid a flat subscription fee each month for all they could eat or all the gasoline they could use. Yet you can pay Netflix $8.99 and watch one movie or all 342 episodes (so far) of “Grey’s Anatomy.” Netflix doesn’t care.

Netflix and Hulu can do this because they sell products with a very low marginal cost. Movies and TV shows are expensive to make. But once that’s done, each new stream costs Netflix little or nothing.

Another product works in a similar way: medicine.

Last week the Senate grilled pharmaceutical officials about the absurd costs of medicines. Public outrage had been building, but it exploded in 2013 with the debut of new cures for hepatitis C. They were very good drugs with very high prices — the first two listed for $84,000 and $94,500 per 12-week treatment. Now, popular revolt is brewing over the costs of insulin, naloxone, penicillin, EpiPens and many other drugs.

The executives commiserated with the American people — and blamed everyone else in the supply chain. Although President Trump has promised tough action, the administration has taken the issue only semi-seriously, talking about measures that have brought down prices in other countries — a little.