Messi was in Milan this week, sparking transfer rumours.
"Let's not become disillusioned. Messi was in Milan for his own reasons with Dolce & Gabbana. He has a €150 million release clause and Barcelona's income is double ours," said Galliani.
A Kaka return is unlikely, suggesting the Brazilian would have to take an unwilling pay-cut if he was to return.
"Kaka? His return is difficult, plus I don't think it is elegant to speak about him before our match with Real Madrid," he added.
"He has advantages playing in Spain, and he has a rich contract."