Yeah, I worry you're right. Those earnings don't necessarily reflect someone living high on the hog or anything, of course. They have a team, although I have no idea how many are on it. If there were 10 developers, that's $10k/month/team member (not accounting for Patreon taking their share, ofc). But if they also live somewhere expensive, that becomes worth a lot less. Let's say they lived in San Francisco. The average earnings there are around $90k/year, so typical earnings are $7500/month. This game would therefore pull in 80% of the average income there for each team member each month. That means you have to cut things in order just to survive with local cost of living.
All of this said, however, I highly doubt any (or certainly not all) of them live somewhere that expensive, and there very likely aren't 10 people on the team. Additionally, if there were 10 people on the team, I would expect far more progress and more frequent updates, especially when you have single-developer games that have both. In summary, it feels like any way you slice it this isn't doing nearly as well as it probably should be. But since I have no idea what individuals are going through (they might all still work full-time jobs and so have limited time, for instance), it's hard to judge with any real reliability.