Dear Xavier,
I don't mean to be a smart*ss, but I think once you look closely again, you'll agree with me that it's not the listing_price.php.
Look at the content of the blue part, please:
Promised, if I use only the published currency US$, it's the very same, except for the "AUD 13,362" and the parenthesis around the US$ amount not showing, naturally.
Then look into the listing_price.php. The lines with that span are #70-#122. There's a lot with discount and tax, and a little bit with "currencyHelper" and, of course, "price_currency_id", but nothing that I can see fit.
In that section, there's not even the expressions ' (' and ')' as would be surrounding the main currency price. (That I find in line #33, but it doesn't help me at all.)
If I do a search for "currencyHelper" across my site, 95 files are coming up. Ok, many have names which are taking them clearly out of responsibility. Anyway, and please trust me again, but I've been through some of these files already, too. Oh, and through all 4 "currency.php" files as well. No luck.
You can tell already from the bits surrounding the blue box in the screenshot that I'm somewhat "familiar" with the general structure of views and editing them... been successfully customizing quite a bit without a glitch. So, thanks for the link, and no offence, but it's like handing the mechanic who needs to get into the transmission the user's manual of the car (and I've been through HikaShop's manuals a lot!)...
So, can someone please give me a another hint? In return I promise that I'll continue not asking questions that are already answered in the documentation or here in the forum.

Thank you once again.