Latest / The Indie Hacker Podcast with Fexingo: Solo Developers, SaaS Side Projects, and Independent Tech / How a Solo Dev Hit 10K MRR With a Recurring Revenue Calculator
Transcript
- Lucas: So Luna, I want to talk about a solo dev who hit 10K MRR with a product that's basically a glorified spreadsheet — but one that SaaS founders are willing to pay for every single month. Luna: A glorified spreadsheet? That sounds either genius or a really hard sell. What's the story? Lucas: The product is called RevRun — it's a web-based calculator that lets you model your recurring revenue. You plug in your customer cohorts, churn rate, expansion revenue, and it spits out projections for MRR, ARR, and LTV. Luna: So it's like a financial model, but purpose-built for subscription businesses. Lucas: Exactly. The solo developer behind it, a guy named Tom — he's a former finance analyst turned coder — he noticed that every SaaS founder he talked to was building their revenue models in Excel or Google Sheets, and they all had the same messy formula errors. Luna: I've been there. I once spent an hour debugging a spreadsheet only to find a cell reference pointing to the wrong row. Lucas: Right. So Tom built RevRun in about three months, launched it in March of 2025, and by September of that year he hit 10K MRR. That's about 350 customers paying $29 a month. Luna: Wait — $29 a month? That's pretty low for a B2B tool. How did he get 350 customers without a sales team? Lucas: Content marketing, but not the usual 'write a blog post about churn' approach. He started a newsletter called 'Revenue Math' where he'd break down the unit economics of popular SaaS companies. Like, he'd calculate the LTV of a Notion customer or the payback period for a Canva subscriber. Luna: So he used his finance background to create a niche content product. That's smart — it positions him as an expert and drives people who care about revenue modeling to his site. Lucas: Exactly. The newsletter grew to about 8,000 subscribers in six months, and his conversion rate was around 4 percent. That's actually on the high side for a paid tool. Luna: Four percent from email to paid? That's impressive. What was his secret? Did he offer a free tier? Lucas: He had a free tier, but it was very limited — you could only model one cohort with up to 12 months of data. The paid version unlocked multiple cohorts, scenario comparison, and export to CSV. The free tier acted as a trial, not a freemium. Luna: So people got a taste, realized they needed more, and upgraded. That's a classic freemium to paid funnel, but with a very clear boundary. Lucas: Right. And Tom made one crucial decision early: he kept the product deliberately simple. He didn't add dashboards, integrations, or API access. Just the calculator, a clean UI, and that's it. Luna: That must have been tempting to build more. I bet users asked for integrations all the time. Lucas: They did. But Tom said no to every feature request that wasn't directly about revenue modeling. He told me in an interview that his mantra was 'if it doesn't change a number in a cell, it's not in the product.' That discipline is probably why he was able to stay solo and hit 10K MRR without a team. Luna: It's the opposite of feature creep. But doesn't that risk losing customers who want a more integrated tool? Lucas: It does, but Tom was okay with that. He calculated that his churn rate was around 3 percent monthly, which is actually below average for B2B SaaS at that price point. The customers who stayed were the ones who really needed a dedicated revenue model tool, not a general analytics platform. Luna: So he traded volume for retention. That makes sense for a solo dev — you don't want to support a thousand customers if they're all high-maintenance. Lucas: Exactly. And that's the key insight I want listeners to take away: you don't need a massive total addressable market. You need a group of people who feel genuine pain around a specific problem, and you need to solve that one problem really well. Luna: It's almost like a micro-SaaS approach. But instead of a Chrome extension or an API, he built a tool that lives in the browser and does one thing. Lucas: Yeah. And the economics work out nicely. At 10K MRR, Tom was making about $120,000 a year in revenue. His only costs were hosting, email service, and occasional freelance design work — maybe $500 a month total. So his profit margin was over 90 percent. Luna: That's the indie dream right there. But what about customer acquisition beyond the newsletter? Did he ever run ads? Lucas: He tried a small Facebook ad campaign in month four, spent about $2,000, and got a cost per acquisition of $120 — which meant it took four months of subscription just to break even. He killed the ads after that and doubled down on content. Luna: That's a great real-world data point. So many people think ads are the way to scale, but if your price point is low, the math just doesn't work unless you have insane retention. Lucas: Exactly. And Tom's story shows that organic, founder-led content can be enough if you're targeting a specific niche. The newsletter was essentially his marketing engine. Luna: I love that he used his background. A lot of founders try to build products in areas they don't know, but Tom leveraged his finance experience. Lucas: That's a great point. It's like the old startup advice: build what you know. Tom knew revenue models, he knew that SaaS founders struggled with them, and he knew how to communicate that pain through content. Luna: So if I'm an indie hacker listening, what's the one concrete thing I should take away from RevRun's story? Lucas: Pick a very narrow, painful problem that you understand deeply. Don't try to be the next Salesforce. Be the calculator that does one thing perfectly. And use content to attract the people who have that pain. Luna: And charge a price that makes sense for a solo operation — not too low, not too high. $29 a month seems like a sweet spot for a tool that saves founders hours of spreadsheet work. Lucas: Exactly. And speaking of things that make sense for a solo operation — this podcast itself is a solo operation in a sense. We don't have a big production team, no advertisers, no corporate backing. It's just us and our listeners. Luna: Yeah, and it's honestly comments and support from people like you that keep us going. If you've gotten something out of today's episode, a couple of dollars a month genuinely makes a difference. Lucas: We keep it ad-free, so the only way this show sustains itself is through listener contributions. If you want to help, you can find us at buy me a coffee dot com slash fexingo. Luna: Even a small amount helps cover hosting and keeps the episodes coming. We really appreciate it. Lucas: Now, back to RevRun — one more thing I want to highlight. Tom recently crossed 12K MRR, and he still hasn't hired anyone. He's thinking about adding one more feature: a churn prediction model based on cohort data. Luna: That sounds like a natural extension. Will it stay simple, or is he finally expanding the scope? Lucas: He told me he's keeping it as a separate module that users can toggle on. So the core calculator stays the same, but you can add a layer of predictive analytics if you want. It's a thoughtful way to increase value without bloating the product. Luna: That's the right call. I think a lot of founders feel pressured to build more features to justify higher prices, but Tom's approach is more surgical. Lucas: And that's probably why he'll keep growing without burning out. The indie hacker lifestyle isn't just about revenue; it's about sustainability. Luna: Well said. RevRun is proof that you don't need a flashy launch or a huge team. Just a clear problem, a focused product, and a willingness to talk to your audience. Lucas: Exactly. And on that note, that's our show for today. Thanks for listening, and we'll see you next time.