15 million for a 30 year old Vucinic is a bit much I think.
We might get such an amount from Zenit. Spalletti is their coach, and he's the guy who brought Mirko to Roma. With the Gazprom money they bought Hulk (for 48m eur), Witsel (35m eur), Danny (26m eur) and Bruno Alves (19m eur). Granted, none of them bar Alves was close to Vucinic's age, but, still, the overall impression is that if Zenit want Vucinic, they could easily pay 15m eur. They regularly overpay for the players they want.