We are certainly bigger than PSG, but we are not richer. From Cavani's point of view there is certainly the possibility that other clubs are more attractive to him given that he has to play second fiddle to Zlatan at PSG. His club most likely don't want to sell him, but they may do so anyway - if a suitable offer comes in. Ergo - interest and bids make the player available, at least in this case.
You really, really think they wanted to sell those players? 🙂