Another financial factor that the “other” group can depend on in funding their schools and places of worship is a far larger population they can solicit for donations. That leads into a somewhat wild guess on my part that a larger general population statistically means a larger population of motivated, wealthy patrons.
Another one of my perceptions (in other words, not based on formal studies I’ve found) is that collecting funds in the typical Jewish community is like shooting fish in a barrel, in that one community must support multiple Jewish non-profit enterprises, like one or more yeshiva day schools, yeshiva gedola/kollel, synagogue, mikveh, food/lodging/medical collections for the impoverished, not to mention emergency campaigns that inevitably crop up.
While some Jewish communities are blessed with some uncommonly wealthy – and charity-minded – members who provide a disproportionate percentage of the financing, less affluent Jewish communities face quite a burden.