Ask HN: How to efficiently calculate subscription price for a webapp?

Say, I have a webapp and I decide to charge customers per month for using this app. I base my price on infrastructure cost, operations cost, labour cost, profit etc.

That price goes up as per the rise in the costs and profit margin. But there is also something that incurs cost for the app developer, and that is data retention cost. For example, say, a customer generates 5gb of data each month. And my cloud provider charges me 10cents per GB per month to store data. So I charge 50cents to that customer. The next month the user again generates 5gb data. Now my cloud provider will charge me for 10gb of data and my cost has increased. That means the price for the customer also has to increase. This will be like increasing the price of the product every month.

Is there a better way to calculate price where the customer generates monthly data and has to retain it?