[skissane]

In my opinion, it is always better style to write US$ or USD than just $ - it is only a couple of extra characters, and it helps avoid any potential confusion

I particularly hate businesses which sell stuff internationally who put $ on their website rather than US$ / AU$ / etc. You can’t assume that just because it is an American company that $ means US$, because some (but far from all) American companies detect the customer is coming from Australia/Canada/whatever and automatically display localised prices. And don’t get me started about the websites that seem to be offering too-good-to-be-true deals on Australian hotels until I realise they are actually showing US dollar prices, but $ instead of US$ makes that non-obvious