Not sure what you are arguing demigan.
The idea behind a barter vs common currency is that people trade for what they need with what others need. The resources for both end up leaving the system via being consumed by the crafting. This generally is going to result in the rarest resources having the highest value due to being the most needed for crafting.
This also results in common materials becoming effectively worthless due to how common they are. Looking at Path of Exile people do not trade for ID scrolls. ID scrolls are the most common dropping currency item next to Orb of Transmutation and Orb of Alteration. No one trades for them because they are so common and easy to get. But a person who gets a mirror can trade for entire inventories of currency items because of how rare and valuable the mirror is and how much return can be gained from it. As it allows one to copy perfect items wanted by a meta build to trade for a lot of currency items.
This results in materials that easily stockpile not being used as a common currency. They have little value because they flood the market. They would only get some value by being important in the creation of complex crafting items or as a resource you can trade to vendors. Even then most would go just drill it up themselves due to how available it is.
Common currency when you look at it is pretty much a system created to allow a nation to gather material wealth under its control from the populace. As the populace puts trust behind the common currency, expecting that currency to be stable and give them a certain amount of resources for a given amount of the currency. When the system has long been used by merchants to manipulate the perceived value of a resource. Not to mention nations would print currency in order to make themselves look more wealthy or to pay for things they did not have the resources to back up. Which is what lead to the situation of The Great Depression and why the Gold Standard was abandoned. Trust was lost, the bubble collapsed, and suddenly it came out that there was just not enough gold to backup the value of the money. Turning the paper money into something worthless until trust was restablished.