AI implementation can start at $30 and go all the way up from there. That includes a subscription to the model you use and a cloud server, or VPS
I recommend using a VPS: if your system runs on your own computer, it stops when your internet or power goes out. The same thing happens if you simply turn the computer off
You can use free open-source models, of course, but in my opinion they don't deliver the quality of work small and medium-sized businesses need
My model and server costs come to around $270 a month: Claude Code at $200, ChatGPT at $20, GLM at $20 and a server at $30. I also pay for services such as ElevenLabs and HeyGen, bringing my total expenses to about $300. It depends on what you need, and that's what you'll pay for
What you pay for at launch
For a budget, it helps to separate the work of implementation from the monthly running costs. The $30 in my example is a starting point for tools and a server, not the price of a complete custom-built system. Setup, connecting services and testing may cost extra
If the job is to help an employee with emails or documents, a subscription to a ready-made service may be a first step. You don't necessarily need a VPS for that: the service runs on the provider's infrastructure. A separate server may be useful for a custom system that needs to work without your computer running

A subscription or usage-based billing
A subscription to an app and access to a model through an API are different ways to pay. For example, OpenAI says ChatGPT and API billing are separate. API costs depend on the model, request volume and features used. Some plans may include credits, so check the terms of the specific plan
A custom system can have several costs at once: model access, a server, connected services and support. Compare options against the same task and expected workload, rather than looking at the subscription price alone

How to estimate your budget
Write down what work the AI should do, who will use it and whether it needs access to other services. Note separately whether it has to work without human involvement and what data it will need. That helps establish whether a ready-made app is enough or a separate system needs to be set up
If choosing tools and estimating costs is still difficult, an AI consultation can help you examine the task and options for a first step. The plan depends on what your business actually needs