I don't think it's about the money, but about having a different culture that's not being respected by the central government. I've recently read about a lot of (very reasonable sounding) Catalan decisions that got blocked or reversed by Madrid.

With this referendum too, this article gives me the impression that it might be Madrid's unreasonable reaction to it that might really drive the independence here. With this kind of response, I don't blame the Catalans for wanting independence at all.