Why Claude and Not GPT
I already had a Custom GPT. "Your Mirror." It worked. People used it and loved it.
So why build something new?
What bothered me about the GPT
1. No control. OpenAI can change the prompt anytime, update the model, remove features. I'm building on a platform that isn't mine. It's like running a restaurant in a rented space — the landlord can raise the rent or terminate the lease whenever they want.
2. No data. When someone uses the GPT, I see nothing. No session data. No bottleneck distribution. No patterns. The most valuable data — what my target audience actually struggles with — disappears into OpenAI's servers.
3. No business model. You can't make money with a Custom GPT. No Stripe. No email capture. No redirect to the Sprint. The GPT is a dead end — a beautiful one, but a dead end.
4. No branding. It looks like ChatGPT. Not like Booster. The user thinks they're using ChatGPT — not my product.
Why Claude
I tested different models. GPT-4. Gemini. Llama. Claude.
Claude won. For one reason: It sounds like a human. Not like a chatbot. Not like a machine. Like someone who actually listens and answers honestly.
With GPT-4, I felt like I was talking to a very clever assistant. With Claude, I felt like I was talking to a sparring partner. And that's exactly what the Booster is supposed to be — a sparring partner, not an assistant.
The tech stack
Built in 4 weeks:
- Next.js — Frontend + API (one framework for everything)
- Claude API (Sonnet) — the brain
- Supabase — database (sessions, users, blog, errors)
- Stripe — payments (Sprint €29, Premium €497, Ongoing €497/mo)
- Vercel — hosting (Frankfurt region, Fluid Compute)
- ActiveCampaign — email automations
- Telegram Bot API — Sprint/Premium delivery
- Meta CAPI — server-side tracking
- Buffer API — auto-posting (LinkedIn + Instagram)
Cost: ~€110/month. For a complete business system that can replace a 5-person team.
What I learned
Own your platform. If you build on someone else's platform, you're a tenant. If you build your own system, you're the owner. Yes, it takes more time. Yes, it's more complex. But you have control. Over your data, over your branding, over your business model.
The Custom GPT was the prototype. The self-built chatbot is the product.
💡 What this means for you:
Whose platform are you building on? Instagram, YouTube, Skool, ChatGPT — all platforms you don't own. That's fine for getting started. But at some point you have to ask the question: What happens if the platform changes the rules tomorrow? If the answer is "my business is dead" — you don't have a business. You have a feature on someone else's platform.