one Spanish gold doubloon (a real life gold coin) at 22 karats weight about 6.8 grams. 500 of them weighed 3400 grams, or around 7.5 pounds. Gold is a dense element and has weight to it. Its not like your characters are carrying around credit cards, or debit cards. You are carrying your wealth with you. And coins have weight. Making them have no weight is illogical.
