UPDATE: Download Woocommerce Extra Price Info Pro Plugin to show extra info on cart & checkout pages.
There is no way to add extra information with the price of the product in Woocommerce. So I created a small plugin which adds an extra box below the price input in edit product page.
You can use it to show the extra information where you are selling quantity based products or you can use it even with other products which comes in packages , e.g $10 (10 pencil pack)
This way your customer will know quantity or the number of items they will get just by looking at the price.