Gillette

King Camp Gillette spent years engineering a disposable-blade razor, and when it finally shipped in 1903 it barely sold. A few dozen handles moved in the first year. Then the company changed one thing about how it made money, and blade sales over the next decade exploded into one of the most copied structures in commercial history. Printers and ink, coffee pods, game consoles, app stores: all descend from what Gillette figured out.

For founders and operators, this is the case that forces a harder question than 'is the product good?' It sharpens how you think about pricing, lock-in, and where margin actually lives in a business. The surprise is that the durable thing customers buy may not be the thing that makes you rich. Read it before you set your next price.