Reports in Italy suggest Milan have made a seven million euro bid for the Serbian attacking midfielder, who has scored 17 goals in 86 appearances for La Viola and has opened contract talks in Florence.
The 21-year-old one-time Manchester United target has two years left on his existing deal at the Stadio Artemio Franchi but the Rossoneri appear eager to make him their marquee signing of the summer after missing out on Carlos Tevez.
Della Valle told the Gazzetta dello Sport: "If we have received an offer, then it was very far away from the player's value.
"The player has expressed to me his desire to stay and we'll see what happens with the contract talks.
"Seven million? That fee is a low one."
Business relations between Milan and Fiorentina have been strained since Italy midfielder Riccardo Montolivo allowed his contract to run down to ensure a move to San Siro last summer, and Della Valle is determined not to let Ljajic employ the same tactic.
"We can't allow another Montolivo situation to happen," he added. "But Ljajic must understand that we have to ensure the wage structure is balanced.
"In terms of his future it's better that he stays here but the situation is clear: if he does not accept our offer then he will be put on the market."