Well, it’s your prudential decision how you spend your entertainment budget. If the money you spend on video games is cutting into your ability to purchase food, insurance, housing, clothing, or utilities, then you’d need to reconsider it. But if you’d rather purchase DLC than go see a film in a theater, or go to an amusement park, then have at it.
I would also keep in mind the impermanence of the content. Even if DLC is promised to last “forever”, it will only be for the lifetime of the game, and you don’t know how long that will be, based on factors both local and remote. So this is not an investment in your future, but a toy for your present.