Nowadays, new cancer drugs typically cost over $10,000 a month, and the price is rising.

With new drugs for rare diseases selling for hundreds of thousands of dollars a year, it occurred to some entrepreneurs to search for neglected old drugs for rare diseases and reprice them. This struck many people as more repugnant than charging high prices for an innovative new drug because there was no research involved.

Mr. Shkreli was not the first to do this. In 2008, Congress held hearings about this practice, focusing for instance on Ovation Pharmaceuticals, which acquired a drug to treat a breathing problem in newborns and raised the price to $1,500 per unit from about $100. There was also Questcor Pharmaceuticals, which spent $100,000 to acquire a decades-old drug for infantile spasms and raise its price from about $40 a vial to over $23,000, with the biggest jump occurring overnight in 2007. Valeant has done this type of thing for several drugs.

Still, Mr. Shkreli captured attention in a way few others have. Part of this was timing. His action was seized on by Hillary Clinton, who was about to make drug pricing a campaign issue in the presidential race. But it was also Mr. Shkreli’s hedge fund background, and his willingness to keep himself in the news with various outrageous statements and actions, some having to do with music and women, not drugs.

“Instead of a nameless company, there is a sardonically smiling face to attach to all of these issues,” said Dr. Aaron Kesselheim, an associate professor at Harvard Medical School and Brigham and Women’s Hospital who has studied drug pricing issues.

Mr. Shkreli has said in his defense that while Turing did not develop Daraprim, it will use the money from the price increase to develop new drugs for serious diseases. He has said that even with the increase, Daraprim will account for a negligible portion of health care spending. He has also said that for many patients, such as those on Medicaid, the price is far less than $750 a pill. And he has said that Turing offers financial assistance and even free drugs to make sure no one goes without Daraprim.

“If you can afford our drugs with insurance, great,” he said in a Twitter post on Wednesday, one of his last before being arrested. “If you can’t, you can have it for free. Our system works.”

That is not too different from the arguments made by the pharmaceutical industry that disowns him. The industry cites the high cost of developing drugs as a reason that high prices are justified. It says that drugs account for only about 10 percent of overall health care spending and the list prices that make headlines are not what people actually pay, given discounting. And it talks about various patient assistance programs.