If you choose a product, and have created a price list for that, you also have the opportunity to choose that. This is useful if e.g. the unit price is different from month to month. In that case, the unit price in the subscription is retrieved automatically from the price list, and you don’t have to do any manually changes in the subscription. Should the price change in the middle of a subscription period, that is not a problem. We calculate the correct price based on how many days there is one price, and how may days you have a different price.