Unsure about the day-to-day situation, I imagine by now they make enough off of the stuff they put out as 100r that combined with very low expenses it's sustainable or close to. In past blog posts they mention taking on contract work for boat repairs.
They seem to be doing a lot of their maintenance themselves so that probably helps too. Still, I am curious about how much in average does the sailing life cost. They give some numbers here and there, so maybe someone more dedicated might be able to come up with a basic estimate.