You would definitely add those as columns in your shopping cart., or at least terms and frequency. You could probably use the existing Price column for the amount.
I'd imagine you only have a few subscription options (weekly, monthly)... I'm not sure if it would be necessary to database all of it. A simple select list on the add to cart page with the options might suffice and then maybe just three columns in your products table "IndividualPrice", "MonthlyPrice", "WeeklyPrice" might do the trick.
What you do or don't add to the database really depends on what actually varies per product. There is no need to add a database field to handle something that really doesn't change on a product by product basis.
You might want to consider a premier support ticket to help you conceptualize the best way to organize your database and cart to support what it is you are trying to do. We can have a more in depth conversation about your business and make sure you are doing things in the best way to support the end result you are looking for.
