The Product report might not be displaying the "correct" revenue based on several factors.
The most common issue people are not aware if is the fact that Wicked Reports is displaying the product price pulled from your CRM. If you offer discounts when you sell products, those are typically negative line items in an order.
To get the correct pricing, you can select the discounts you use for specific offers or products by going to the "Order Items" dropdown, shown below.
Products are listed by the "Products" heading. See the second image for "Order Items" which are discounts, promo codes etc.
Product Items Screenshot
Order Items Screenshot
"Order Items" which are promo codes, discounts etc. Shown Below. By selecting an entry under "Order Items" you can see what the dollar amount of the discount was, and how many times it was utilized by your customers. 
Additionally, you can also select "Net" which will filter out refunds, voided payments etc, show below.