If Vidal is allowed to come (big if though), with the price 50m, I would say DO IT. It will cause a domino effect. Who wouldn't want to play with a world class teammate? Keita, Schick will agree our offer in 1 second for example. With Vidal, we have the strongest midfielder in Italy (even more than Rube). Vidal, Vecino, Gags, Kondo, Valero.
As a consequence, a world-class player will also boost income revenue. More attendance to the stadium, more jersey sales, more marketing values...and most important: Champions League.
But I could not see it comes true tbh. Sadly, Ancelotti is the worst person we have to deal with when asking for a player. He hates Inter apparently. No other one has told explicitly to the media that "I would never coach Inter because I am a Milanista" like him.
Even when Rummenigge pushes for the deal, all Carlo has to do is simply answering "I need him to implement my tactics".