Nobody tells you the real bill of running an AI app in production. Here's my honest breakdown, with real numbers, so you can plan without surprises. Spoiler: starting costs way less than you think; the spend scales with usage, not before.
The four spending buckets
Your spend splits into four: hosting (servers and functions), domains, AI models, and payment fees. Cold, a small app can cost almost nothing. The trick is knowing which bucket spikes and when.
Hosting and domains: cheaper than you think
With Vercel or Firebase, hosting a small app usually falls in the free tier or a few dollars a month. Domains cost 10 to 15 dollars a year each. That part is almost never the problem — you can launch your first product spending practically zero on infrastructure.
AI is your surprise cost
Every model call costs. In a prototype you barely notice; with real users it spikes. The key to controlling it: use 'flash' or cheap models for 90% of tasks, reserve the expensive models for what truly needs them, and cache repeated responses. That's where profitability is won.
Don't pay for scale you don't have yet. Start on free tiers, measure before optimizing, and upgrade only when usage asks for it.
And payment fees (Stripe and the like) only hurt when you finally charge — which is exactly when it stops mattering, because it means you have revenue. It's the 'problem' you want to have.