> given that folks calculate cost based on recurring payments

That’s very true for mortgages, but in my experience this isn’t how student loans work. Nobody I knew before college had any idea what their loans would cost on a monthly basis once they went into repayment, and I don’t think it was disclosed to me (or I forgot).

Also unlike my mortgage, my loans have trivially changed repayment plans. I changed some of them several times based on my economic circumstances without refinancing, which makes nailing down a single payment kind of hard, even if the interest rate hasn’t changed.