The coinage of the realm may vary from world to world,
but the effect is the same:  without money, you're in
quite a bind.  Since you need cash to pay for equipment,
buy food, and pay for training, money is integral to
success.  Your Charisma determines the cost of what
you buy and sell, so the races that are more brutish
usually find it difficult to sell their gleaming new
sword when their nose drips.  

1 platinum = 100 gold
1 electrum = 10 gold
10 silver = 1 gold
100 copper = 1 gold

Expect currencies (and exchange rates) for each world
in the future.