Italian clubs will do everything to get the 'option to buy' and not 'obligation to buy' and if it is the latter they'll want to pay in instalments over a period. I remember with us trying to sell Aquilani in 2010, Season long loan to Juventus + agreed an option to buy end of season for 13m, (13m they wanted to pay over three years!) that's how stingy they are.
They refused to take up the option of course, he came back, went out on loan again to Milan where they too tried it on. A season long loan with option to make move permanent if he made 25 appearances, what did Milan do? stopped playing him after 23 games. This is why I'm glad we don't engage in these type of negotiation deals with Italian clubs anymore, if your in for their players you just have to pay the money up front like Roma with Alisson, and demand the same in return, else they just dictate to you what they want.