Spices

The spices back in the 1700s were of great value because there were no rifrigerators to refrigerate the spices. The countries that had control of the spices were basically in control of spice trade because the spices themselves were so limited, that the country could charge the buyer a huge amount of money to pay and still get the money because therer are not many places where you can get it for a lesser price

Importance of American money

The gold and silver that was imported by Spain ensured that the price of the goods and mercandice would not fall. In some occasions the price would actually rise either due to a serplus of the goods or the people were buying and therefore the companies tried to get more money. If the price were to fall, this coul be very harmful to the sellers because the would, in the long run have to buy more goods before they had the money to sell anything
If the price level were to fall, however the merchants might not be able to sell enough to pay back all that they have and would have to go bankrupt. This basically says that withouut American money the economy of other countries could and would have a significant fall.