If commodity prices are calculated relative to currency, then during import/export, market goods shouldn't be able to trade normally (because each country's currency value is different. When calculating import/export transaction prices, they should be standardized into gold. This should lead to situations where countries with high currency value but lower commodity prices export to countries with low currency value but higher commodity prices. However, I haven't observed this happening in the mod). If commodity prices are calculated relative to gold, then in Bulk Supply Agreements, the commodity price is calculated entirely based on currency.