This article explains how to configure the pricing information for products in your Magento Go catalog.
Cost:Represents what an item actually costs you (the store owner). It is used only in the back-end, and can be used for generating revenue reports.
Tax Class: Taxation may vary from product to product and from one tax jurisdiction to another, as well as in the shipping of different products. Magento Go provides the options None, Taxable Goods, and Shipping. Select the appropriate option for the products you are selling.
Special Price:if you will be offering discounts or promotions for particular product, simply add a special price in the allocated field. You can define the promotion period by entering the start and end dates for the promotion in the To and From field dates, using the calendar icon or by manual entry