What is the amount of Zakat due on 500,000 Lira, which is the price of selling the citrus fruit harvest season, after deducting expenses amounting to 250,000 Lira?

There is no Zakat on citrus fruits themselves, nor on their selling price, unless the price reaches the Nisab after deducting expenses and a full year has passed on it. The Nisab for currencies is the equivalent of 85 grams of gold or 595 grams of silver, and the obligatory Zakat is 2.5%.