Canadian here and doing this for French and English has not been a major deal breaker. One of the qualifications we put on our documentation team was being bilingual.

You can also NOT use typical screenshots for documentation but rather have templates screenshots that contain no text and then layer the text over top of those and use things like language selection in the browser to load the correct language.

Employee training can be simplified by headquartering out of one country and having a "primary" language that you work out of day to day.

For many early startups having full fledged customer support (call center style) isn't likely anyway, doing it via chat / email / support tickets can be translated or you can diversify your support hires to cover the languages you officially support.

So is there additional costs - definitely - are they enough to impede and side rail a startup... likely not, and if they are that startup likely wouldn't have been able to succeed anywhere else either.

You're getting push back for the same reason you are shaking your head at the other poster - they are making it sound like it's free, and you're making it sound like it's going to crush someone.... it's slightly more effort with possibly a greater reward if you are able to do it properly.