Out of curiosity why didn't you just scale the cost proportionately to the volume change? That would leave gold at exactly the same cost-to-value/useage ratio as before.
The only limiting factor would be the cost of a single piece of gold being too high for whatever it was being used for, which seems a fairly minor concern.
The only limiting factor would be the cost of a single piece of gold being too high for whatever it was being used for, which seems a fairly minor concern.