No, prefixes, as in kg. Money, as we have seen in this thread, does not use SI stuff at all, so talking about it this way is awkward, since $100k appears to have an SI "suffix" when technically it carries an SI "prefix." But US people usually do not say "100k USD"; they believe $ always means USD. People in other countries using $ know their dollar sign is likely to be confused, so are more likely to say "100T ZWD" etc.
Yeah, it's kilodollars, just written "$100k" rather than "100 k$" conventionally. But it's fairly clear that what's being multiplied is the base currency unit (dollars, euros, whatever). For historical reasons currencies give the units via a symbol before the number, instead of a letter after it: €10, $10, £10.
Depends on the country. Most people in the eurozone use "10 €", not "€10". However, when adding SI prefixes most people would append the prefix to the amount, rather than prepending it to the unit e.g. "100k €".
