Give them the razors, sell them the blades!

Reviewing a classic case — take it from there.

In the early 1990s, Gillette started handing out free shaving kits to men celebrating their 18th birthday. The idea was simple: hook guys at the age when they were deciding on their permanent shaving brand.

Here's the rough math:

90% of men didn't notice. But the 10% who got into Gillette spent $40 a year for the next decade replacing blades — all for a gift that cost just $10 to mail.

Gillette mailed 2 million letters annually, bringing in $80 million in revenue, with $60 million in profit.