You are correct in saying that QF dont recieve a cent from the cost of the cadetship.
Infact it costs them in terms of administration, uniforms etc.
It is Qantas's intent to employ everyone who is selected for the cadetship. The only person who has control over employment is the student themselves, if you're mature, do they work and put in the effort then there will be a job waiting for you at QF (dependant on the fact that QF are recruiting at the time).
Goodluck to all applicants (I believe they're expecting over 1000 this year, for around 30 places).
And if anyone wants any info feel free to e-mail.
(PS-Been ages since I've made an appearance on Pprune, good to be back! hehe)