How Castmagic grew an AI app from zero to $120K MRR in ten months

Executive overview

Building AI tools for existing workflows removes friction rather than creating novelty — and that's where sustainable growth comes from. Castmagic solved a real problem the founders had themselves: repurposing podcast content with AI.

Three founders, no outside funding, launched in two weeks through AppSumo, scaled to 120K MRR in ten months.

Solve your own problem, distribute through creators, and keep investing in output quality.

Finding the idea

• Blaine hosted a podcast and couldn't delegate show notes to a VA — the context was too complex
• AI unlocked a solution: repurpose any audio or video into content automatically
• Key principle: doing things constantly surfaces problems worth solving, often with bigger implications than expected

Launching on AppSumo

• Two-week deadline forced a rapid build; accepted an imperfect product
• Launched a lifetime deal to build brand, users, and feedback — not for recurring revenue
• Result: ~$350K revenue, ~10,000 users, one of AppSumo's most successful launches

Building and tech choices

• Built with Elixir and Phoenix LiveView — stable, scalable, front and back end in one language
• Landing page in Webflow using templates to free up dev time for the core product
• Prioritised the product over polish in the first two weeks

Marketing with a lean team

• One marketing manager, supported by contractors per vertical
• Outreach to creators: scrape platforms, find adjacent industries, build volume before negotiating rates
• Created a Notion doc of content concepts so creators could work without a strategy call
• Rule: keep marketing spend below 20% of revenue

Creator and affiliate growth

• Identified businesses that scaled through affiliates and reverse-engineered their approach
• Paid some creators; used affiliate structures for others
• Tested CPM-based payouts to find viable channels before scaling spend

Pricing and margins

• Subscription billed monthly with a usage cap
• Tested price points empirically rather than modelling upfront
• Monitors LLM and transcription costs continuously to maintain margin

Why Castmagic won

• Solved a real, existing workflow problem — not a novelty
• Built brand by partnering with the right creators early
• Kept investing in output quality; customers can tell when shortcuts are taken
• Positioned as a workflow platform, not a point tool — harder for ChatGPT to displace

Key metrics

• 120K+ MRR, growing 20%+ month over month
• Net churn: single digits
• Marketing spend: under 20% of revenue

VC vs bootstrapping

• Two founders had prior VC-backed experience; chose to bootstrap this time
• Time spent pitching VCs was replaced with talking to customers and building
• Fundraising is a separate skill set — learning it before generating revenue gets the order wrong
• Advice: build something customers pay for first; take VC to accelerate only if it fits

Team and operating model

• Founders split by lane: product, marketing/growth, engineering — minimal overlap
• Alignment and complementary skills matter more than convenience or proximity
• Async by default during the week; quarterly in-person week for roadmap and alignment
• Monday and Friday 30-minute standups; keep calendar clear to focus on shipping