Outrage over the cost of insulin has driven much of the political conversation about high drug prices, with reports of patients dying because they could not afford it.

In February, the Senate Finance Committee sent Lilly a letter asking for more information about how it sets prices for its insulin products, including Humalog. The letter noted that taxpayers spend more than $1 billion a year for Humalog through Medicare and Medicaid and said, “When one insulin product costs the taxpayer more than $1 billion in one year, the American people ought to know how the company prices its product.”

Sen. Ron Wyden, the ranking Democrat on the Senate Finance Committee, said in a statement Monday that the investigation into Lilly’s insulin prices would continue. “The company’s decision to offer a generic version of a several decade old drug will be part of the investigation,” he said.

The story of insulin, many say, is a salient example of how the drug pricing system is broken. Over the years, industry intermediaries known as pharmacy benefit managers have negotiated ever-deeper discounts for insulin, yielding savings for the insurers and employers that pay the bulk of drug costs. Insulin manufacturers have responded by raising their list prices in an effort, they say, to please the benefit managers, who keep a percentage of the discounts they pass along.

The list price of insulin has gone from about $20 per vial in 1996, when Humalog entered the market, to about $275 per vial today. Humalog patients typically use about two vials a month, Lilly said.

The result is a yawning gap between the list price of insulin — which people who are uninsured must pay — and the net price that insurers and employers pay.

Enrique A. Conterno, the president of Lilly’s diabetes division, said Friday that the list price of the authorized generic will be comparable to the net price the company regularly offered to insurers in exchange for standard placement on their formulary, or the list of covered drugs, although he did not specify a dollar amount. But he said the company provided deeper discounts to insurers that give Humalog preferred treatment, which typically means lower out-of-pocket costs for patients.