Human speech has a bit rate of around 39 bits per second, no matter how quickly you speak. assuming reading is similar, I guess more "dense" tokens would just take longer for humans to read.
https://www.science.org/content/article/human-speech-may-hav...
Sure, but that link has Japanese at 5 bits per syllable & Vietnamese at 8 bits per syllable, so if billing was based on syllables per prompt you'd want Vietnamese prompts
Granted English is probably going to have better quality output based on training data size