Which way [is the phrase "You don't have 10$, yet alone 5" or "You don't have 5$, yet alone 10?"]

Two unrelated thoughts.
1: One tradition comes from the halls of science. The other comes from the halls of business. One is logical and consistent. The other is ad hoc & inconsistent. I leave it to your knowledge of human nature to decide which is which. :slight_smile:
2: In times gone by folks developed different symbols syntaxes to differentiate stuff they were copying by hand. They didn’t have too many different syntaxes available, but that was fine because they didn’t have too many categories of things to write.

Fast forward to today with the explosion in categories, measurement systems, nomenclatures, etc. Against that combinatorial explosion of complexity we now find consistency to be a virtue, not a source of possible ambiguity. Common syntax also helps lots when the intended audience is often a relatively inflexible machine.

I’m the same. I tried to think of a logical reason why but can’t either.

Yeah, but in Quebec specifically, they use dollars and commonly put the symbol after the number. So one can’t even make the counterargument that dollar signs (as compared to euros, etc.) always go in front. The OP’s usage would be perfectly cromulent there.

I remember seeing 10 USD more often than USD 10.

Interesting.

Per ISO 4217 - Wikipedia the standard the defines the codes doesn’t define whether they’re prefix or suffix. That’s up to local language authorities.

Having said that, in US usage the codes for USD and for all other currencies are prefix to the numbers.