Sometimes you want to create a product with one price for a certain period of time that changes to another price after that time period expires. In order to do this, you would use the "Trial" option when creating the product to cover the initial period.
If you create a product in this way, when the customer purchases that product, the product description on the checkout page will include this information. For example, if you create a product that costs $100 for the first 60 days and then $20/month afterwards, the product description will appear as follows:
This information is output by the SmartTag [MM_Form_Data name='productPriceDescription']. In the WordPress Editor for the Checkout Page, you can delete this line from your checkout page and hard-code your own Price Description.
You would change this:
into something like this, where you just type in what you want output:
It's important to keep in mind that when you take away the SmartTag, the checkout page is no longer dynamic. Meaning that regardless of the product information that's being passed to it, it will always display this new product description. Because of this, the best practice is to Create a Custom Checkout Page for this specific product and alter the product price line on that custom page.