Limitations on Mexican Flights

Why do they use $ for both currencies, just asking for trouble.

By “both currencies” do you mean “three currencies”?

C$, M$, US$

Or maybe more…

Dollar is the name of more than 25 currencies. The United States dollar, named after the international currency known as the Spanish dollar, was established in 1792 and is the first so named that still survives. Others include the Australian dollar, Brunei dollar, Canadian dollar, Eastern Caribbean dollar, Hong Kong dollar, Jamaican dollar, Liberian dollar, Namibian dollar, New Taiwan dollar, New Zealand dollar, Singapore dollar, Trinidad and Tobago Dollar, and several others. The symbol for most of those currencies is the dollar sign $; the same symbol is used by many countries using peso currencies.

https://en.m.wikipedia.org/wiki/Dollar