Cost to Add a Mobile App to an Existing SaaS: React Native, Expo or PWA Priced for a Web Product Already in Market

Why a mobile app for a live SaaS costs less than a new MVP

A new MVP means building everything. An app for an existing SaaS is mostly a new screen layer on top of systems you already run. So be careful with any quote that prices your app as if it were a new product. If it includes a new backend, ask why. Here's what you already have, and what the app still needs:

• Database and business logic. New MVP: build it. Mobile app for an existing SaaS: already exists, reused.
• User accounts and login. New MVP: build it. Mobile app for an existing SaaS: reuse your auth provider.
• Billing. New MVP: build it. Mobile app for an existing SaaS: usually stays on the web.
• API. New MVP: build it. Mobile app for an existing SaaS: reuse it, sometimes add a few endpoints.
• Mobile screens and navigation. New MVP: build it. Mobile app for an existing SaaS: build it.
• Push notifications. New MVP: optional. Mobile app for an existing SaaS: usually the main reason to have an app.
• App Store and Google Play submission. New MVP: needed. Mobile app for an existing SaaS: needed.

React Native, Expo or PWA: which one fits a SaaS already in market

Short definitions:

• React Native is a framework for building iOS and Android apps from one JavaScript codebase. The app renders real native screens.
• Expo is a toolkit on top of React Native. It handles builds, store submission and over-the-air updates, so you skip a lot of native setup.
• PWA (progressive web app) is your existing web app with an install option. Users add it to their home screen from the browser. It doesn't go through App Store review.

React Native + Expo or PWA: how they compare

How the two options compare:

• Listed on App Store and Google Play. React Native + Expo: yes. PWA: no, installed from the browser.
• Reuses your existing code. React Native + Expo: your API and auth. If your web app runs on React, part of the logic too. PWA: your entire web frontend.
• Push notifications. React Native + Expo: full support on iOS and Android. PWA: supported, but on iOS only once the user adds the app to their home screen.
• Camera, biometrics, background tasks. React Native + Expo: full access. PWA: limited, depends on the browser.
• Feels like a "real app" to your customers. React Native + Expo: yes. PWA: close, but users can tell.
• Best when. React Native + Expo: customers ask for "the app" by name, or you need push, camera or Face ID. PWA: you mostly need mobile access and your web app already works well on a phone.

Our default for a live SaaS

Our default for a live SaaS is React Native + Expo: iOS and Android from one codebase, plus push, plus store presence. A PWA makes sense if your customers only need quick mobile access and won't look for you in the stores. If that's your situation, we'll tell you on the call. Sometimes the cheapest answer is to fix the mobile layout of the web app you already have. For a deeper look at how mobile builds work with us, see our mobile app building guides.

What our mobile app build includes

Here's the list from our services page for the mobile app build:

• iOS + Android from one Expo project
• Auth, onboarding, core loop
• Push + RevenueCat / Stripe when you sell
• TestFlight + Play submission support
• 100% source + 2-week fixes

What the core loop means for your SaaS

For a SaaS already in market, we confirm what your app needs once we've read your API. The "core loop" is the one or two things your users open the product for. In a field service tool, that's checking today's jobs and marking them done. In a CRM, it's looking up a contact and logging a call. In an analytics product, it's checking the dashboard and getting an alert. You get a fixed quote before we start. The code goes on your GitHub, and you see progress every week.

The 4 things that add work to your app

Four things add work to an app built on top of a live SaaS: an API that isn't ready for a mobile client, complex login, offline mode and selling subscriptions inside the app.

1. Your API isn't ready for a mobile client

Many SaaS products render pages on the server, or their API was written only for their own frontend. A mobile app needs clean endpoints that return data. How to check: ask your team whether the main screens of your product can be loaded through API calls alone. If yes, the app plugs in. If no, a few endpoints need to be added first. That's real work, so we scope it before we quote.

2. Login is more complex than email and password

Email login, Google login or a standard auth provider like Supabase or Auth0 is simple to reuse. Enterprise SSO through SAML, or several custom identity providers per customer, adds work. How to cut it: for v1, support the login method most of your users already use. Add enterprise SSO when a specific customer needs it.

3. Offline mode

"Works without signal" sounds small. In practice, the app has to store data on the phone, queue changes and resolve conflicts when it reconnects. That's often the biggest single addition to a mobile scope. How to cut it: start with read only offline. Users can see their last loaded data without signal, and edits wait until they're back online. Many field teams are fine with this for v1.

4. Selling subscriptions inside the app

If users can buy or upgrade inside an iOS app, Apple's App Store rules generally require Apple's in-app purchase system. Google has similar rules on Play. That means a second billing flow running next to your Stripe setup. How to cut it: many SaaS apps don't sell in the app at all. Customers pay on the web, then log in on mobile with the account they already have. This keeps your billing in one place. If in-app selling matters to your model, we set it up with RevenueCat. Store rules change, so we check the current ones against your model on the call. Not sure which of these applies to you? Book a call. In 30 free minutes, we look at your API, tell you what adds work, and you get a fixed quote before we start.

How to scope v1 of your SaaS mobile app

Don't port your whole web product. A good first mobile version does fewer things than the web, and does them faster.

• 1. List what users do on mobile today. Look at your mobile web traffic and support requests. Those pages are your first screens.
• 2. Pick the one moment push notifications matter. A new lead, a job assigned, a payment failed. That's often the whole reason the app should exist.
• 3. Leave admin and settings on the web. Team management, billing pages and integrations rarely need a mobile version in v1.
• 4. Decide on billing. Web only, or also in the app. This one choice changes the scope more than any screen does.
• 5. Share your API access early. The sooner we can call your endpoints, the sooner we can confirm your fixed quote.

Get a fixed quote for your app

After launch, you can keep adding features with our Continuous Growth Support. Ready to give your customers an app? Book a call and get a fixed quote for your iOS and Android app before any code is written.

How much does it cost to add a mobile app to an existing SaaS?

Less than a new MVP, because your backend, database, auth and billing already exist. Our price for an MVP app on web, iOS and Android is Fixed at $3,460. For your SaaS, you get a fixed quote before we start, after we look at your API.

Should my SaaS build a PWA or a native app?

Build a PWA if your web app already works well on a phone and your users don't need push notifications on iOS or a store listing. Build a React Native + Expo app if customers expect to find you on the App Store and Google Play, or if you need push, camera or biometrics.

Can a React Native app reuse my existing backend?

Yes. The app talks to your current API and auth provider, so your database and business logic stay where they are. Sometimes a few endpoints need to be added for screens your web app renders on the server.

Do I have to use Apple in-app purchases for my SaaS app?

If users buy digital subscriptions inside an iOS app, Apple's rules generally require in-app purchase. Many SaaS apps avoid this by keeping billing on the web, so users log in with an account they already pay for. We check the current store rules against your business model before quoting.