You also have "free" options:
LibreTranslate - Github (I have used it, its surprisingly quick but lacks on understanding - deepl for instance understand a lot better the context) but is free
Free G translate - github (I haven't personally used it - however people seem very happy with it)
Also, as of today, you have options available like LLaMa3-70B or LLaMa3-8B (which is very cost-effective and easy to run).
You could develop a plugin that set's a multi-lingual chatroom, you could structure the translation service using a series of microservices. This way, you can isolate the translation tasks from the main game processes, ensuring heavy translation loads dont impact performance, each microservice would handle a part of the translation process independenly, making the system highly scalable imo. instead of using traditional HTTP requests, which can slow down interactions, use WebSockets. a more stable connection between the player client and your translation server. you can also cache the most commonly used translations to retrieve them instantly reducing the need to process the same thing over and over again, you can easily handle interpretation for the variations with NLP (NLTK - is very good). After a while you'd have enough data to scale your system more efficiently