Skriniar, 23, has made a big impression since moving to Inter from Sampdoria in the summer of 2017.
The defender's performances have led to reported interest from the likes of Manchester United, Bayern Munich and Barcelona, with speculation that Diego Godin could join in the summer from Atletico Madrid only heightening the belief that Skriniar could be released.
Inter, however, are determined to keep their man, and as talks over a new contract continue Spalletti announced that he was not for sale.
"Skriniar is staying here, he is out of everybody's price range," the coach signalled following Inter's 6-2 Coppa Italia demolition of Benevento on Sunday.
"Nobody can afford him."
Skriniar himself moved to dismiss transfer talk in the past week as he struck out at a Slovakian newspaper which speculated over a possible move.
“You write things that you don’t even know," Skriniar posted on his Instagram story.
"You are sh***. Now write an article on this."
Brazil centre-back Miranda is another player who has been linked with an exit from San Siro, and Spalletti cut a more cautious tone when referring to his future.
"Miranda has not said anything to be me, he is a serious professional," he added.Inter return to Serie A action following the winter break on Saturday, when they will host Sassuolo.