I think the truth is that no one will ever be abe to guage the profitablity of a LCC that is a sunsidiary of a main carrier because many of the LCC fixed costs come out of the mainline budget, admin, maint, crewing admin, IT etc etc.
How much prifit will jetstar make, its at the whim of an accountants pencil.
That said. i like the concept, different level of service/product according to my taste at the time. Just like should I buy a Ford or a Jaguar........they are the same company.