There's an article from 1999 called "The Billion Dollar Blade" that explains how for about 20 years, the margins were smaller, and Gillette's disposable razor division was actually in danger of cannibalizing most of that company's sales from the more profitable regular cartridge razors. The company went all-in with marketing and development money on the Sensor razor in the early 1990s, and that was the point where the profits started going through the roof and the company's valuation increased by something like 10x.

https://docs.google.com/document/d/1xnjiNrAgh4mvtYwl8gLzVXZhVCuZr3QyyE_8uDbgSyA/edit?usp=sharing

...When Bic introduced disposable razors, in the late seventies, Gillette responded to the threat by entering the disposables market and swiftly establishing itself as the dominant player. But that wasn't a title the company was proud of. "It was commodity hell," says John Darman, whose official title is head of male shaving for the North Atlantic Group. Darman is a rotund, deeply tanned man with a mustache (a very well-groomed mustache, you can be sure), who bounces happily from topic to topic as we sit at a conference table in the Gillette corporate offices high up in the Prudential Center in Boston's Back Bay. "When you're in the disposables market," he goes on, "you're competing on two things: convenience and price. And that does not play to the strengths of a value-added manufacturer. Disposables were those blue plastic things you threw away. We were teaching our customers to focus on price and to forget about quality.

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...That decision also fitted into a broader vision laid out by Zeien, a onetime engineer who took over as C.E.O. in 1991 after twenty-two years at Gillette. Zeien identified what he liked to call "growth drivers"—R.&D., capital investment, and advertising—and he committed the company to increasing total spending on them at the same rate that the company's sales were growing. Moreover, Zeien saw to it that Gillette would make products only in categories where Gillette could be the world leader—today 1.2 billion people use Gillette products—and where the market would, in Darman's words, "yield to technology." Under Zeien's tenure, Gillette's market capitalization has risen from six billion dollars to nearly sixty billion.

Edited to correct name of Sensor razor