I use ChatGPT as well as mckaywrigley/chatbot-ui with GPT-4, and I rack up $300+ charges every month using my own version of ChatGPT, so it's way more expensive (I do roughly the same number of conversations in each). The only reason why I use it is because I can pump in more context than what ChatGPT allows. But if you're using a cheaper model / lower usage then maybe it'd be less expensive. You could also try Perplexity