I disagree. Tevez is a great player, one who works his ass off for the team. I would love him here but he is a luxury, and as you rightly pointed out would cost too much. Over and above, we don't really need him at this point in time.
Regarding your comment about Argentinians in Serie A, all I have to say is look at Sivori, Batigol, Zanetti, Samuel, Crespo, and the list goes on. They have all been highly successful.
Not all Italians are that good. Some players like De Silvestri, Marchionni, and Quagliarella are average at best.