Cheapest Invention that made millions,rather billions

I recall as a kid been told that if someone was clever enough they could expect to make millions. A prime example of the foregoing was the English inventor and businessman Percy Shaw (April 15, 1890 – September I, 1976). This was the guy who invented cat's eye, the reflective studs in the center of the road which enables vehicles being driven on dark nights to remain in the correct lane. In 1934, he patented his idea, and on March 15 the following year, established a company to manufacture the things.

He named his firm Reflecting Roadstuds Ltd, and being such an excellent creation, anyone would have imagined that the authorities would have been falling over themselves to purchase the items. Alas, very few appeared interested. Then came the Second World War, and to deny enemy bombers easy targets, Britain extinguished all the lights. I have heard it said by folks who were around at the time, that more people were killed and injured on the dark British roads than were harmed by German bombs. Now, demand increased dramatically, and soon the company was turning out 40,000 units per week.

As to how Shaw came up with the invention, there is a story which may or may not be true. One foggy night (so the tale goes), he was driving home from the pub. The road was hazardous. It had sharp turns, and on one side, a steep bank atop of which was a wooden fence. Shaw would have crashed through that fence, and with devastating consequences, had a cat not been sitting there reflecting the vehicle's headlights with its eyes.