King Camp Gillette was selling bottle caps for a living while he worked on an idea that would spawn so many other great ideas (and some slightly ridiculous ideas, like the 5-blade razor, but we can't really blame him for arms races like that). He didn't have a particular passion for shaving - he just wanted an idea for something that would make him money. He recognized the golden rule of sales - if you can sell something that people need and use and throw away - but then buy again - you have a way to make money for life. There were some alternatives to the straight razors that were everywhere at the time, but the blades for them still had to be forged, which meant they were expensive to produce and to buy.
Gillette's genius was two-fold. First, he realized that if he could sell a razor with disposable blades, he could keep customers for life as they continued to buy replacement blades. Second, to make a better profit margin, he realized that he needed to find a cheaper way to produce the blades, and after a lot of work, he found someone who helped him to develop a process for stamping blades our of sheets of steal.
Gillette's razors sold for $5 apiece, and blades sold in packages of 20 for $1.
This is where Gillette's legacy really takes off. Yes, he was the pioneer who was responsible for the Gillette Company, which now includes Oral-B, Braun and Duracell after being purchased by Proctor and Gamble in 2005. To business students, however, he is also the father of a powerful business model, called either freebie marketing or the razor and blades business model. The idea was to give people the razor (or the lamp, or the DVR, Prince CD, etc.) which will in turn yield profit when the customer comes back to buy razor blades (or kerosene or installation or concert tickets) from the same company. Gillette still uses this model (they used it on me just last week, when I bought some inexpensive razors and got a nicer model for free - which I loved and will probably have to buy again), but so do countless other businesses that give something away for free but by giving it open up a new customer prospect.