Anyway, they need copper and silver pieces IMO to divide up the currency and make gold actually worth something again. And it doesn't have to be divided up into multiples of 100 like our currency, it could be in 20s for example, with 20 copper being worth 1 silver, and 20 silver being worth 1 gold. Copper would be used to buy things like food, cheap alchemy ingredients, and inexpensive arrows. Silver would be used to buy rooms at nicer inns, inexpensive weapons and armor, and good alchemy ingredients. Gold would be used for houses, horses, fine weapons and armor, and powerful magical items.
If we went by the base 20 currency system like I suggested, and 1 copper piece was assumed to be equal to 1 gold currently, then gold would be worth 400 times as much as it currently is. If you think that's too drastic then you could double prices and make copper worth 1/2 of what gold currently is and 1 gold could be 200 times as valuable as it is currently.