Pet Rocks were a surprise hit in the ‘70s. The Solution: The Pet Rock. He told People magazine in 1975 that he was selling 100,000 Pet Rocks a day, making 95 cents profit … In 1976, over 1.5 million people purchased them for $4 a pop. The Return: $15 million profit. It’s one of those ideas so simple you think, “Man, why couldn’t I have come up with that?!? Gary Dahl, the Pet Rock's inventor, became an overnight millionaire.

“Your PET ROCK will be a devoted friend and companion for many years to come.”. The Pet Rock was also cheaper than a real pet -- at $3.95, much cheaper. That's a reasonable price to be the clever one at the party who can always claim to have the lowest of all low-maintenance pets. In 1975, the pet rock sold 1.5 million units at $3.95 a pop. Dahl estimated he had sold 1.5 million of them at roughly $4 each. As long as everyone and their brother haven't bought the same gimmicky product and can't crack the same joke. Rocks enjoy a rather long life span so the two of you will never have to part — at least on your Pet Rock's account." !” Most people will chalk up the runaway success of the pet rock as luck.

The creator, Gary Dahl, became a multimillionaire within six months. And even though it was a fad that lasted only 6 months, it made the inventor, Gary Dahl, a millionaire overnight.