Don't forget that in addition to the 25% "loan fee" the balance of the FEE-HELP debt is increased by the CPI % each year for outstanding balances.
Assuming that the amount repaid to jetstar over the 6 years is taken from gross salary and therefore remaining salary falls beneath the threshold for FEE-HELP repayment, during the initial years the FEE-HELP debt will grow by approx. $97k (ie an additional 12k) assuming no FEE-HELP is repaid in the first 6 years and a CPI of 2.5%.
Consequenty the cashflow will not be as severe as has been suggested.
FEE-HELP will be repaid over a much longer period although the total amount paid will increase significantly.