The sugars in the grapes do not freeze, thus creating wine with higher sugar concentrations. Ice wine production is risky because many grapes do not survive the cold temperatures—resulting in ice wines being generally expensive.
The sugars in the grapes remain liquid even at low temperatures, resulting in a higher concentration of sugar in the wine. Ice wine production is fraught with danger because many grapes are unable to withstand the harsh winter conditions, making ice wines more expensive as a result.