Most stories on the register have currency converted into the local currency of the journalist (although Japanese Yen should have been listed first, followed by the conversion). Richard is Australian, hence AUD. Also, The Reg has quite an audience in Australia, so for "many readers" AUD works just fine.
In general, many people have a vague idea of different currencies, if anyone has ever wanted to buy from overseas or go overseas (most People I would think) then a quick look at a currency website, or watching the news occasionally will help (I'm Australian, and have had no trouble keeping up with the usual "currency X => GBP" that goes with many stories here).
As a general rule at the moment, $1AUD buys:
- roughly $1USD
-roughly 60-70 british pence
-roughly 75-80 Japanese yen
-a small cottage in europe (except Germany)
-a politician in Greece