Folks should fully understand this common assertion. The vast majority of drugs do not cost anywhere near $1B to develop. See the balance sheet of biotechs and pharmas.
If you add up all the expenditures of biotech and pharma development for X years, plus all the basic pharmaceutical and relevant biological research performed at all colleges, universities, private labs, and public labs, and clinics, plus the administrative costs, then divide it by the number of newly approved medicines for same number of years, you get a high figure like that. But that is relevant to society, not to a specific biotech or pharma.
Another way to understand it: it includes the costs of everything (and not just failures).
So it is the averaged financial cost to society of developing drugs. It's not the average cost for a biotech or pharma to develop a drug.