All aside from Mbappe were already at better and bigger clubs at the time of their transfers. Speaks volume.
Mbappe was smart in his move though. He's now starting for a European heavy weight. However, when he needs to leave to future his career I don't think those slave drivers will make it easy for him or his club.
Scenes if he left on a free.
It's a little bit more nuanced. PSG under Qatar was a bigger project than Napoli, Milan needed money and pushed Thiago Silva out, Mbappé cameback to his hometown, Neymar is probably a money move but it could also be linked to Barcelona's inner context and Alves was reportedly offered more money by City but he wanted to join Neymar.