Here is my suggestion for global trade. Let the free market determine the price. For example, every item has a max price of 50k. Every item, or 1000 items, added to market drops price by a percentage. Have players be able to buy whatever they want but price is set by supply and demand. After 24 hours in market sellers can decide whether to sell to daniel at a set price or percentage of market price. This will make rare items more expensive but will make players have to decide exactly how to value items that they buy.