Don't know too much about the CX cadet program. However a quick comment on the Qantas one. All it entitles you too is a priority path to employment. You have to use one of their schools (cost is significantly more than a normal flying school - remember you are paying, not the company). You are then on on industry placement until you have sufficient experience to be selected for a jet conversion. If the industry suffers a downturn, your job with the mainline can be delayed for years in some cases previously. When this happens you still are not earning a salary.
So yes you get normal pay rates when you join the main company however to get their you have outlayed a significant portion of your own money first (in the order of $100,000 AUD)