If you will look at any yeshiva budget, (I am not referring to the MO Schools which charge between two and three times what yeshivos in Brooklyn or its surrounding areas charge, they have a whole different model) you will see that the tuition chrged does not cover even the average costs. A large portion has to come from elsewhere.
Bottom line is, your tuition is likely not even covering the costs to educate your own children, let alone other’s children.