Razors were bundled with everything from Wrigley's gum to packets of coffee, tea, spices, and marshmallows.
The freebies helped to sell those products, but the tactic helped Gillette even more. By giving away the razors, which were useless by themselves, he was creating demand for disposable blades.
A few billion blades later, this business model is now the foundation of entire industries: Give away the cell phone, sell the monthly plan; make the videogame console cheap and sell expensive games; install fancy coffeemakers in offices at no charge so you can sell managers expensive coffee sachets.