Why the key is yours
You connect your own OpenAI key and the AI modules use it. That is a deliberate design: there is no marked-up AI credit to buy from us, you see exactly what the usage costs at the source, and you can change model or revoke the key without asking anyone.
It also means the honest answer to the cost question is that AI usage is between you and OpenAI.
What AI replies do well
Questions phrased in a hundred ways with the same intent, which is most of what a busy group asks. A person writing in their own words gets an answer in their own language, and nobody had to predict the exact phrase in advance.
Where a fixed reply is better
Anything with one correct answer: your opening hours, delivery area, prices, where to order. A fixed auto reply cannot drift, and the questions that cost you money if answered wrong are exactly the questions you want unable to drift.
A good setup usually uses both: fixed answers for facts, AI for everything else.
What else runs on the same key
Sentiment analysis, content moderation, image generation, voice transcription and text to speech are all part of the same AI set, and all use your key. Turning them on is per channel, like every other module, so you can run AI in one community and not in another.
Setting it up carefully
Start with one channel and watch the answers for a week before widening. Keep your fixed replies in place while you do, because the AI will not improve an answer you had right already. And set a spending limit in your OpenAI account rather than relying on the group being quiet.