Pricing can be affected by quantity, i.e., unit priced, or the price could vary based on quantity which is called volume pricing, or the total cost can be the sum of different costs within different quantity ranges which is tiered pricing. Or the cost for something can simply be a fixed price that may vary according to options - think of each option as a dimension or additional column in a database table.
Suggest that you begin by considering a Pricing Data class with properties such as ProductID, FromQuantity, ToQuantity, Price, FromDate, ToDate.
User would enter additional properties such as RequestedQuantity.
When computing the ultimate price other properties would be needed such as Discount and DerivedPrice.