PSG probably has something similar, they are spending a few million a year acquiring very young players, players under 18, and then playing them in their youth teams and in cup games to give them experience and that's how big clubs keep being big. They do not only buy expensive players but spend it on the team itself as well.
I believe that PSG will only improve as this season progresses, and as we saw against Vannes they’re playing much better football, but there’s definitely lots of scope for improvement considering their star studded squad.
Also grooming young player’s is a wise way to save money on future transfers, and I guess PSG has also realised that they don’t need to spend big during each transfer window, and lastly it’s quiet a possibility that new big stars may emerge from their youth academy in coming year’s.