I think quite a few people imagine the JWs as being wealthy.
Depends on your perspective.
In the US, for example, a typical US native wouldn't think so.
But for a recent immigrant, one who came with virtually nothing and now works 60-80 hours a week and sends 80% of their earnings back home, seeing other JWs "just like me" with nicer clothes, a functioning rust-free car, and a house, well, JWism seems like the path to a much better life. So why not listen to them?
Virtually all growth in the USA is in foreign language congregations, and virtually all of that growth comes from immigrants who are the target of those congregations.
I imagine it is similar in other countries.