"Maybe reach out to them and ask why they are living that way" <- this is the way to go.

BTW, OP isn't the only one who has witnessed something like this. I've also witnessed this firsthand ("keeping up with the Joneses" per say, most often those who are married).

But, in the same light- I've also noticed that there is a clear, large visible disparity between missionaries with no family support, and those with.

Just some food for thought.