What is the average land area of ​​the cities in which stores that purchased products for a unit price of 998.30 are located?
average land area = Divide (Sum(Land Area), Count(Land Area))
SELECT AVG(T2.`Land Area`) FROM `Sales Orders` AS T1 INNER JOIN `Store Locations` AS T2 ON T2.StoreID = T1._StoreID WHERE T1.`Unit Price` = '998.30'