MRR is useful when revenue repeats. It becomes misleading when a product is sold once, through several stores, or with a mix of lifetime and subscription purchases. You still need a way to see momentum; you just need to name the model honestly.
Separate the kinds of money
Start by separating subscriptions, one-time purchases, refunds, taxes and platform fees. A $39 Mac app sale is valuable, but it does not create another $39 next month. A $9.99 subscription may create a smaller first payment and a more predictable base.
When several storefronts are involved, record the source and settlement date. Cash received, gross sales and recognised revenue answer different questions. A simple founder dashboard should make those differences visible rather than hiding them behind one optimistic number.
Make a comparable monthly view
For one-time products, take the last three or six months of net sales and divide by the number of months. This is not MRR; call it average monthly net sales. You can compare it with your costs and use it to decide how much runway a promotion or release can support.
If you want a planning scenario, add a separate projection with explicit assumptions: new customers, price, churn for subscriptions, and seasonality for one-off sales. Label it as a scenario. The value is in seeing which assumption deserves your attention.
Track the question behind the number
Numbers become useful when they lead to a decision. Are you deciding whether to improve onboarding, raise a price, add a subscription, or publish another guide? Keep the metric close to that decision. A smaller honest dashboard beats a beautiful number you cannot explain.