$ value and value $ are both seen in Canada for example, former being more common in English, latter in French

Canadian conventions vary by language. In English, I’ve only ever seen $ then figure.

• Canadian government price indexes
• BBC report on Canadian supermarket prices
  • photo of multilingual price tag
  • price comparison table shows currency symbol £ C$ $ precede figures

The ISO currency code can go after (eg, 1 USD, 1 CAD).

It’s a national convention: Wikipedia claims that in all English-speaking countries (and most of Latin America), the symbol precedes the amount.

If they’re a non-native English writer, I guess that would explain it. An awful lot of people in the US seem to do this, too. 🤷