Perhaps the title of this thread is not reflective of the OP’s real question. I gather the OP means to ask, “How can we manage to tuition if we are not on a substantial income?” A corollary to that question is how to cope with the heavy and pressing demands of the yeshivas. But the question is not the same. The title implies that yeshivos charge too much. I am not the field of school administration, and I also doubt that any two schools will have very different profiles that would result in very different tuition scales.
When I am short on money, everyone else appears to be rich. And when they ask me for anything, I judge it to be greed. No, that is not okay. But that is human nature, one of those midos we need to overcome.
The real issue is that yeshivos have tended to use parents and their tuition obligations as an area of leverage. These yeshivos exist on a spine of donations, and many have a welcoming hand for government funding. They create budgets that include tuition, and this is the only piece where they can exert force. Yes, if the balance is outstanding, your child will be denied entry or admission. Nice, no. Menchlich? Of course not. Is this compatible with their stated mission of providing as much chinuch of the highest quality to as many talmidim as possible? No. But yeshivos are business as much as a professional, a grocery store, and any other private enterprise. And they can use this leverage because, well, because they can.
Ideally, there would be a huge measure of tolerance to give a break to those parents who experience financial struggles. Again, midos we wish existed. Maybe some yeshivos do behave this way. Some food stores and take outs do function this way, and these are praiseworthy. But the average store does not allow poor people to shoplift, and the average yeshiva does not tolerate those who do not pay tuition. Again, what is fair? My opinion won’t matter much.
My advice, focus on what you do have, and do your best at living up to your responsibility to provide chinuch to your children. It is not your business or mine that other parents take vacations or have nice cars.