Every parish around Philadelphia, small or large, urban or suburban, contributes large amounts of money to its school to keep the tuition low. The tuition rates (and per capita parish contribution) were not materially different at the school in suburban Malvern when I lived there, which is in one of the top 5 school districts in the state of Pennsylvania.
I do know that they're both subsidized by the Diocese, and that St. Joe's keeps track of who's at Mass and how much they give. This was esp. evident when we signed my daughter up for pre-K CCD (to start this fall) -- they confused us with my in-laws, who do NOT give any more. (My MIL is a liberal moonbat who says she is "culturally Catholic," but won't give or attend Mass because she doesn't like our Monsignor, disagrees with the Pope, and believes that "all curch donations go to perverts.") They called us to tell us that our daughter couldn't go, because we weren't "active members," until I showed up with a fistful of cancelled weekly gift checks.
In the end, we're probably sending my daughter to Villa Maria lower school -- ata whopping $6,875/yr. (But the IHM's are outstanding.)