Dunk has caught the eye of several clubs having started every game for the Seagulls, who top the Championship after dropping just two points in their opening six games.
Poyet told BBC Sussex: "Sometimes you cannot keep players forever. We couldn't do it with Andrew Crofts or Elliott Bennett.
"They'll have to pay. I'm not bothered. Everybody's got a price. Dunky has got his price because of the way he plays.
"If he goes to play in the Premier League, I can't control that. I can control him while he's here."