Billionaire Elon Musk's new invention is a flamethrower, and it's stirring up a firestorm while selling like hot cakes. Musk's company, The Boring Co., has already sold 15,000 in pre-orders, according to his personal Twitter account. They are $500 each, and the flamethrowers will be shipped out in the spring. Musk even appears in an Instagram video promoting the flamethrowers. The idea of selling a flamethrower to the general public seems so off-the-wall, many people are asking if it is a joke.