One example might be Jordan Mechner, who wrote Karateka between the ages of 18 and 20, which went on to sell 500,000 copies. One of his journal entries mention

One example might be Jordan Mechner, who wrote Karateka between the ages of 18 and 20, which went on to sell 500,000 copies. One of his journal entries mentions he got 15% royalty, and one of his videos mentions that the original retail price was $34.95, so he may have made a couple million from it.