Further, at the rate they are paying/saving for their and their children's education, they don't need to do that very long before they no longer need to make the payments.

To present it as steady state is misleading.

EDIT : as other people are pointing out, there seems to be lots of double counting (high insurance premium + full contribution to HSA) and assumptions about steady state costs (cars,clothing) that are either misleading or a lifestyle choice that the family is making.