I built my own Monarch-style finance dashboard with Opus 5.5 for less than $20

SharkFin is my personal finance dashboard inspired by Monarch. I can connect bank accounts through SimpleFin and then link those to Actual Budget to feed the backend. The great thing about Actual is that its open source, allowing me to store the data locally and have full ownership over it. The React based front end was built with only 35% of my weekly limit (Claude Pro $20/month) using Opus 5.5 medium . I was very happy with what I could get out of medium and never felt the need to bump up reasoning from there. I had it research existing financial dashboards, pull screenshots, and work off of those to build out the UI. Biggest advice that I could give is to focus on getting one part of the app to work really well and build on that momentum. I started with the cash flow page, built it up, and then added all the other pages after. One of my favorite parts of the app is how customizable it is. I own a couple of properties and Opus made it so easy to set up a separate page to monitor each property individually. From there, I can see how much I'm cash flowing month/month and what my biggest expenses are all in one spot. I had it only feed the cash flow (or losses :)) into my main budget to prevent polluting it. Super useful. To be clear, Claude (Opus 5.5, through Claude Code) wrote nearly all of the code: the React front end, the server that talks to Actual's API, the container setup I used to host on Docker. I decided what to build, tested it against my real accounts, and asked for changes until it worked the way I wanted. Everything runs locally in Docker, and nothing is exposed to the internet. The screenshots come from a demo mode with made-up data. I wrote the post text here myself. I have no intentions of selling this, but could be convinced to open source it if there's enough interest. It's crazy how easy it is to build these kinds of things out now