Currency

Currency (通貨, Tsūka) is any item accumulated and used to make purchases. While coins are a common medium of exchange that the inhabitants of the New World and the YGGDRASIL Players share, the value differs between the two.

New World Economy
In the New World, four primary metals are utilized as the monetary standard and valued in increasing value: Copper, Silver, Gold, and Platinum. About 1/4 of the copper coins were made from brass. Platinum coins were rarely used with the exception of merchants and nobles. In addition to that, there does exist financial institutions supported by the government. For example, the Imperial Bank located in the Baharuth Empire. Trusts in the form of metallic plates are used by the banks within the Empire, similar to that of a cheque. Trade between nations exists through numerous official and unofficial channels; platinum in particular is used in international trade.

In the Web Novel, all Trade of Currency, was said to be marked with the symbol of the God of Business which is the wheel. And on the other side is the symbol of the merchant guild that issued the currency.

If gold coins were too heavy to be used as payment, big transactions were typically made with gemstones and the like. Some countries used gemstones to make a type of extremely high-value currency called gem coins, or they made coins of mithril or adamantite, or “gold plaques” which had value beyond their weight.

Exchange Rate
The exchange rate between the Re-Estize Kingdom and the Baharuth Empire is 1:1.

Japanese World of 2138 Economy
If you converted the price of a copper coin from the New World into Japanese Yen, its worth would be about 1000 yen. One gold coin is also equivalent to 100,000 yen.

On the other hand, according to the Web Novel, YGGDRASIL currency of 1 gold was estimated to be worth the estimated value of 1,000,000,000 yen in the real world.

YGGDRASIL Economy
Unlike the inhabitants of the New World, players used only one type of metal as currency: Gold. In the past, YGGDRASIL's coins went through two conversions. Originally, the gold coins had the face of a man sealed upon them, before Valkyrie’s Downfall Event. It's current form has the profile of a woman, possibly a Valkyrie. YGGDRASIL gold had multiple uses, such as a medium of exchange for purchasing items, guild house maintenance, as a component in magic scroll and potion manufacture.

After the Great Tomb of Nazarick's transfer to the New World, all the coins and valuables stored within the Treasury have been transformed into actual gold. Ainz has also discovered that compared to the gold coins that are used by the New World inhabitants, YGGDRASIL coins are worth at least twice as a standard gold coin in the New World, but due to the artwork on them probably five times more.

Trivia

 * It is unknown if New World coins other than gold can be used in Nazarick's NPC resurrection system. Thus, Pandora's Actor has been charged in appraising all outside valuables in order to determine their value.
 * Ainz keeps an original coin of YGGDRASIL as a keepsake of his younger days of playing with his guild members together.
 * Three gold coins were enough to feed a normal family for a whole month in the New World.
 * By the New World standard, 30,000 gold coins was viewed as a craftsman's 300,000 days, 821 years worth of money.