Not wanting to get dinged for $20/mo? Ability to use offline for local home automation (eg: "given a verbal input request, determine the home devices in scope and their on/off state" => "given the current devices state and the verbal request, generate a list of home assistant actions to perform"), using a custom model for the above, etc.
OpenAI (& peer) API pricing is honestly quite cheap - I spend way less than 20$ a month for my needs. On the other hand, ChatGPT offers a different experience, so I pay for that too.
