At a 100K salary, over 24 years you would pay 72K. The same cost of 72K as a loan at 6.8% paid over 24 years would amount to $146,229.96 with total interest paid of $74,229.96

That's more interest than the cost of the loan. You would have to average more than 203K a year in salary in order for this to be the wrong choice. The average student isn't going to come close to that. Do you really expect that you'll be making more than an average of 203K over the next 24 years?