The real cost of a personal AI agent breaks down into two quite distinct line items, often confused in online discussions. The first is the server cost: the machine running the agent continuously. For personal use, a small VPS is plenty (2 vCPU, 4 GB of RAM), at a public rate of around $4 to $5 per month from a host like OVH — this need barely grows with usage intensity, since it's the language model doing the work, not the server itself.
The second item, much more variable, is inference cost: every message sent to the agent and every response generated consumes tokens billed by the language model provider. This cost depends on two things: the number of exchanges per day, and the model chosen. An economical model can cost less than $0.10 per million tokens, while a more capable premium model can cost several dollars per million tokens — a gap that directly affects the monthly bill depending on usage intensity.
We built a calculator that makes both costs transparent, based on public pricing tables (OVH for the server, OpenRouter for the models), with the calculation assumptions clearly stated, so anyone can honestly estimate what an agent would cost running entirely on their own.
By comparison, a managed service like Hermes Agent France charges a fixed, capped amount depending on the plan chosen (€49, €89, or €199 including tax per month), which includes the server, the agent, maintenance, and support — with no billing surprise in a heavier-usage month.
