Sure. He made many millions of dollars within the first couple years of releasing it. That's why he can pretty much do whatever he wants, including continuing to work on the game without charging additional money for it. And of course, it keeps selling more copies, and will for many years to come, so he has tons of money continuing to flood in.
He certainly seems like a pretty grounded guy, and it's nice that he tries to be cool about stuff, including not gouging the player base for more money. Being an individual has huge advantages compared to being a corporation, in some ways. A corporation would pretty much be obligated to maximize profit. He can just be pleased that he brings joy to millions of players, and has already made a fortune.
I'd give a separate extra upvote for the cat participating, if I could!