[deathanatos]

First, I totally agree that that argument is terribly worded. Nonetheless:

a. against that median $30k income, you're building equity, which is net worth. Someone on $30k might be paying rent (and they're not able to afford a mortgage), and thus, that money is just a flat expense.¹

b. w.r.t. student loans, someone making $500k/yr is going to be able to pay vastly more into that loan, and pay down the principal a lot quicker, which will translate to lower interest costs, vs. someone making $30k/yr. (Depending on whether this is parents or the student, if that rate could be refinanced or not, etc., I would also think a $500k/yr might also net you a lot lower interest rate due to the risk of your inability to pay being significantly less.)

¹and yes, houses have their own issues, such as maintenance, and some of that mortgage is going to interest.