Build cost gets quoted carefully. Running cost gets waved at. Then month two arrives with an Apple invoice, a Stripe deduction and a hosting bill nobody budgeted, and the product feels more expensive than it was sold as.
Here is the honest list, from platforms we run ourselves.
Hosting
Far less than people fear. A dedicated vCPU box with fast NVMe storage in Germany runs a website, an API and a database comfortably for a small monthly figure, an order of magnitude below the equivalent on AWS once egress is counted.
The number that catches people on the big clouds is traffic. On the hosting we use, the traffic allowance is generous and flat, so a good month does not produce a surprise bill. Budget for a backup target as well, because backups on the same machine are not backups.
The app stores
Apple charges an annual developer fee per account. Google charges a one-off registration. Small numbers, but two things follow from them.
First, they should be in your name, not your agency's. If your developer account belongs to whoever built the app, you do not control your own listing. Second, someone has to renew the Apple fee. An expired membership pulls your app from the store, and it always expires at an inconvenient moment.
Payments
This is usually the largest running cost, and it is the one most often left out because it is a percentage rather than a bill. Card processing takes a percentage plus a fixed amount per transaction, and it comes off every sale for ever.
Model it against your actual volume before launch. On a low-value, high-frequency product the fixed element per transaction matters far more than the percentage, and that can change what you decide to sell and in what bundle.
The small recurring things
- Push notifications. Effectively free at normal volumes, which is why nobody mentions them. Fine.
- Transactional email. Receipts, resets, confirmations. Cheap, but not nothing, and it scales with users.
- SMS, if you use it. Genuinely expensive at volume. Reminders by push and email cost close to nothing; the same reminders by text add up fast.
- Machine translation. Priced per character. A catalogue that changes daily across six languages is a real line item.
- Domains and certificates. Trivial, and worth owning yourself rather than through a supplier.
The one people forget entirely
Someone maintaining it. Not new features, just staying still: security patches, an operating system that goes end of life, a payment provider changing an API, Apple requiring a new build to stay listed.
That work exists whether or not it is budgeted. If it is not, it gets done in a panic at a worse price, usually by someone unfamiliar with the system. A modest monthly retainer is not an agency upsell, it is the honest price of owning software.
A rough shape
For a typical connected platform, a website, an app and an API, the fixed monthly running cost is smaller than most founders expect and is dominated by hosting plus maintenance. The variable cost is dominated by payment processing and scales directly with revenue, which is the right way round.
The mistake is not that these costs are large. It is discovering them in month two rather than putting them in the plan.
Planning a build? Ask whoever is quoting for a year one running cost alongside the build price. If they cannot produce one, that tells you something. We include it as standard. Get a scoped proposal