You misunderstand how football in Italy works. Money is running low in the Serie A however big names attract memberships and sale of shirts. So what the big clubs are doing is to aim for relatively big names who are either unsettled or they are in the end of their contract. Nani, Honda, Llorente, Tevez, Balotelli.....you get the grip.
I don't think that Juventus are interested in Nani at the moment. He had just signed for United which makes him untouchable. However if we offered him to them as part of Marchisio's deal then thI think they would be interested. Think about it, Nani is at the right age, he's got great technique and can play on both flanks. He does lack workrate but thats rated more in the EPL then in the Serie A. On the other hand Marchisio stands in the way of Pogba + will allow them the financial clout needed to keep Vidal. He's also at the right age to sell.