Averted in the case of Baravada, where the currency is pretty much dime-sized gold coins and gems of widely varying sizes.
With Strings Attached: Played with and subverted in a couple of cases:.
There was a period of economic chaos before one pony managed to create a new silver-based currency system, which Equestria continues to use to this day. After Corona, though, use of gold coin is considered blasphemy, and possibly treason.
RainbowDoubleDash's Lunaverse: Before Celestia became Corona, Equestria used to use gold for its currency.