Formula Bot: An Excel-Formula AI Built During Parental Leave Hit $23,000/Month — Zero Lines of Code, $5,000 in Marketing

Dollar figures in this article include an approximate conversion at $1 = ¥150.

What was built in two weeks of parental leave became $345,000/month

David Bressler, based in Orlando, Florida, is a director of analytics with over 12 years in marketing analytics. In May 2022, his second son William was born, and he went on parental leave. In July, he started experimenting with generative AI and discovered the no-code development tool Bubble.io.

What he built there was “ExcelFormulaBot” (now Formula Bot) — a tool that converts natural-language instructions into Excel formulas. Development took “just a few weeks.” He wrote zero lines of code. His original expectation was modest: “worst case, I’d have a tool for myself that made my own job dramatically faster.”

That tool reached $23,000/month (about ¥3.45M) in about six months. Bressler kept his day job. Headcount is zero.

The numbers, up front

A note on the numbers: the source article’s headline says “$26K/Month,” and the profile section shows “$220,000 revenue/mo,” but the most current specific figure confirmed in the body text is “the most recent month hit $23,000.” This article uses the $23,000 body-text figure. The $220,000 profile figure is likely an order-of-magnitude typo.

Timeline of the ramp-up

What was the actual turning point — not virality, but ending the free period

Reddit exposure was certainly the origin point. A TikTok influencer described it as “a site that feels almost illegal to know about,” and outlets like PCWorld, Inc.com, and BGR.com sent backlinks. But virality alone didn’t make this business work. During the free, unlimited period, revenue was “a few thousand dollars from a few hundred people” in donations, and behind that, OpenAI API bills were piling up. More traffic meant deeper losses.

What changed the trajectory was a staged tightening of the free offering. The sequence went like this:

1. Launch free and unlimited
2. Require login
3. Cap the free tier at 5 uses per month
4. Turn unlimited use into a $6.99/month subscription

Bressler describes this as “letting people taste unlimited use first.” There’s numerical backing behind it. The 5-uses-per-month cap is enough for 97% of users, and only the remaining 3% are frustrated by the limit. In other words, this design lets 97% of users keep spreading the word for free while carving out only the 3% as the paying base. Because the free crowd is never alienated, monetization happens without sacrificing viral reach.

The before-and-after is clear. The free period ran on donations, a few thousand dollars from a few hundred people. The instant paid access went live, the first sale landed in five minutes, and within a few months revenue reached $14,000, then $23,000. On the same traffic, only how it was captured changed.

Why it worked, structurally

He occupied the side of a search term that didn’t exist yet. Bressler notes that search terms like “Excel AI generator” and “excel formula creator” simply didn’t exist before this product appeared. When new search demand is born, the party that created that demand is the one who ranks first for it. Latecomers trying to take the same term need to build content and backlinks to catch up. He was already there from day one. The lasting value from going viral wasn’t the direct sales it produced, but the search rankings and backlinks it left behind.

A $6.99 price point eliminated the decision-making step. About ¥1,050 requires no corporate approval process and no household budget discussion. He priced the decision cost away, designing for a low conversion rate against a huge base, a billion-plus Excel users worldwide. In practice, all that’s needed is a slice of the 3% within that base.

No-code brought the cost of failure close to zero. Combining Bubble.io with the OpenAI API meant initial investment was effectively nothing, costs were limited to API usage and hosting. His premise, “worst case, I get a tool for myself,” held because all he had at risk was time. Two things aligned at once: the free time that parental leave provided, and no-code removing the need for capital.

Word of mouth acted as an amplifier. In his words, “one plus one equals three.” When one person discovers the site, they tell someone else. Excel formulas are the kind of headache that gets shared at work, so the transmission path runs directly through people’s jobs.

What didn’t work, and the limits it’s operating under

• PPC advertising: acquiring leads at $10 each, but Bressler explicitly states “still hasn’t broken even.” Recovering a $10 lead cost against a $6.99 subscription requires a meaningful retention period, and they’re still running it while figuring that out.
• Influencer campaigns: spending $200–$3,000 per person, but he admits measuring effectiveness is difficult. The observation that there’s no dedicated influencer market for SaaS is, read the other way, an admission this is still trial and error.
• Team plans at 2%: higher-value business accounts aren’t growing. He states B2B is a future priority, but for now, dependence on individual subscriptions is heavy.
• AI accuracy: raw model accuracy started around 85%. The remaining 15% of inaccuracy is being patched on the product side.
• Variable cost base: OpenAI API fees sit at the center of cost. Usage growth means cost growth — the free-tier cap functions as cost control in itself.

What’s reproducible, and what isn’t

What’s reproducible is the design side: replacing a task you personally repeat in your own job with AI. Giving away free and unlimited first, then pulling back a cap afterward. Setting that cap at “a level where the vast majority won’t be bothered.” Pricing low enough that no decision-making is required. Removing the cost of failure with no-code. None of this demands capital or technical skill.

What isn’t reproducible is the timing. Summer 2022, right when the OpenAI API had just become accessible to individuals, and “AI that generates Excel formulas” didn’t yet exist in the world. A moment when Reddit was still reacting to novel tools, and the search terms were still wide open. That window doesn’t reopen in the same shape. Add to that his 12 years of hands-on marketing-analytics experience, which gave him a sharp read on Excel users’ pain points. That also doesn’t transplant directly.

And it’s easy to forget that reaching $23,000/month on $5,000 of marketing spend is a story that comes after weathering losses during the free period. He took a hefty API bill on the chin before arriving at the current monetization design. It wasn’t cheap from the start. The design was refined until it became cheap.

Related reading

• PDF.ai’s Damon Chen — another record of an indie build using AI APIs that took off
• Photo AI and levelsio — a case of quickly capitalizing on a window when generative AI first opened up