A developer vibe coded a paid budget app in a weekend with Codex and says it made about $20K in its first month
Bryl Lim built Tarsi as a demo for a university talk, charged once instead of a subscription, and grew it through a public Facebook group.
Subject: Tarsi (Bryl Lim)Paid-upfront budget tracking app for iOS ($4.99) and Android, with optional subscriptions for cloud and AI extras
Case Overview & Background
Bryl Lim, from the Philippines, built Tarsi as a live demo for a university talk about vibe coding and published it because he already had a developer account. People started buying it. Tarsi is an offline-first budget tracker with a tarsier mascot, sold as a one-time purchase. He told the Tap & Swipe podcast it made roughly $20K in its first month across iOS and Android and topped the paid charts in several countries, and he has repeated the approach with a trip planner and a workout tracker.
How AI Is Used
Step-by-Step Process
He used Codex on a React Native template to ship the first version in one weekend.
Charging once avoided paywall setup, and he says the paid charts have far less competition than the free ones.
With no server or database, the core app has no running costs.
Users post requests in the group, he logs them in Apple Notes and builds the most wanted ones with Codex.
Customer Acquisition & Distribution
Limitations, Risks & Failure Modes
What may not apply to you, and what could go wrong:
- The revenue figure is self-reported and was not independently checked
- First-month sales may not hold; the podcast puts daily sales at around $350 later on
- Paid apps need a steady stream of new buyers rather than renewals
- Chart rankings in small paid categories can change quickly
Key Takeaways
- A one-time price can stand out when most apps push subscriptions
- Shipping a small working app quickly can uncover demand you did not plan for
- A community space inside the app can double as free marketing and a feedback loop
Sources
Tap & Swipe: How to Top the Paid App Charts With No Ads and No Subscription
Note: Podcast episode page with a written summary. States the roughly $20K first month, the Codex weekend build, the paid model and the Facebook group growth.
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