As all professions and jobs in life, it depends. You cannot spend one week/month to make a simple game and expect thousands of dollars. To stay on topic, my latest project where i managed and produced a 2d game, cost me around half a grand and i am in process of selling for few hundreds more. There are different methods to consider, like ads or self-launch, so it depends what platform and targets you aim at, or better said the type of game you work on.
You should share your game or plan of your gig. Good luck!