I really like Matri, but to say that he is worth more then 15 million euros is funny shit. Think from another view, would you like your club to pay 15 million euros or more for Matri? Nah you could easily get better players for that money. He is a good player but not near worldclass. If you pay big cash for a player you would either want them to be worldclass or have potensial to be worldclass, Matri isen't worldclass and will never be
To be said, I would easily give away Matri in a deal for Cavani, the same goes for Quagliarella for a good offer I would have no problem to see him go.