Qantas needs Jetstar, and Jetstar needs Qantas.
Maybe, for a passenger on-carriage point of view. From a stand alone view point? Qantas, from a "pays the bills" viewpoint pays it's own bills and still makes money. Jetstar? Where would they be if they were buying their own aircraft, or perhaps paying their own fuel bills? I certainly think Jetstar needs Qantas far more than Qantas needs Jetstar.