You're assuming that doesn't get re-charged onto Jetstar, minus adjustments for inter-company transactions. If you can prove that, I'd be interested to see it. And surely any other provider would also have some spares on-hand for one if their customer has an AOG, even if it comes from a pool?
QF Engineering fought hard to not have the parts on their books, insisting that they should be in JQ’s inventory but an instruction came from a very high level that they must be held in QF International inventory. You wouldn’t insist on that if you were subsequently going to charge JQ when the parts are used.
When you take into account the previous history, such as the promise (when they were operating A330’s) that JQ would pay for their A330 simulator time which was total BS. The then head of QF Flight Training repeatedly tried to get payment from JQ but after a while he was told that no money would be forthcoming and if he didn’t stop his submissions he would lose his job.
Also, all the fuel uplifted by Qantas Group aircraft in HNL is paid for by QF International, yet JQ International still doesn’t make a profit despite many subsidies. If they were making a profit, Joyce would show it on the books but he keeps all those figures hidden.