Here's an example of a professional stenographer dealing with 300+ wpm days (search "300wpm" in this page): https://jadeluxe.wordpress.com/2014/12/30/year-in-career-201...
Yes they do. 230 wpm is close to the upper limit for natural speech, but bursts of speech at that rate are quite common if the speaker is in a heightened emotional state or they are trying to convey a lot of information quickly.
Research into subtitling (closed captioning) by the BBC and OFCOM found that live programmes normally have bursts of speech at over 200 wpm. The BBC article below includes a sample clip of a presenter reading a news report at 230 wpm; while it sounds rushed and the presenter occasionally stumbles over a word, it does not sound completely unnatural.
https://www.bbc.co.uk/rd/blog/2015-09-how-fast-should-subtit...
https://www.ofcom.org.uk/__data/assets/pdf_file/0011/41114/q...
Average speaker is 150, an auctioneer is 250-400, the fastest person. The fastest talkers male and female can recite over 500,600 words per minute.
People can certainly and some people while exited/upset may.
Someone speaking a language like Chinese, where most of the words are single syllables, could probably speak a lot faster than someone speaking, say, German, where the words are often super long.
That's just my mostly uneducated guess, though. It'd be interesting to see some real-world comparisons of this.
I realise 500/600 looks like 5/6, but 500,600 reads to me as 500600. Maybe | is a good unambiguous character to use for "or".
As Y_Y already indicated:
> I realise 500/600 looks like 5/6 ….
If we're going to fuss about typography, these things:
> 500-600 wpm; 35-75 Kph; 2-3 grams.
are hyphens, and you want an en-dash: 500–600 wpm instead of 500-600 wpm.
Edit: I stand by this. Auctioneers do provide a good counter example but much of what they say is just repeated phrases.