Main point already covered (no discount for pre-existing hours), but the one thing not covered that mightbe worth considering if you have a PPL and then go integrated - sponsored or not - is that learning from scratch to CPL/ME/Ir standard with no prior experience is a big hill to climb. Far from impossible (god, even I managed it!) but I would say, from my experience that I feel my confidence and ability to absorb the new information in every flight would have been a LOT higher had I had a lot more hours than I did when I started.
What I'm trying to say is that a PPL won't save you cash explicitly, but it may well save you having additional training (that you need to pay extra for) and it may well help keep your lesson scores up - which in turn helps breed the confidence that is all important for your flight tests.