The shinobi world, which had never had any concept of economics, had now spontaneously developed a system for regulating goods. That alone proved how prosperous its commodity economy had become, and how closely the Five Great Shinobi Villages traded with one another.
The people who first laid that foundation were neither Shingetsu nor Tobirama, but the Konoha ninja Tobirama had dumped in distant lands-ostensibly to guard important resources, but effectively to exile them.
These people took advantage of their positions to either send resources back to Konoha or bring Konoha's goods to their postings.
Things that were commonplace where they originated became remarkable treasures in foreign lands. Some shinobi with a good head for business smelled an opportunity and simply started buying and reselling goods between the two places.
One easy example was the Konoha ninja stationed in the Land of Wind, who had been the first to do this.
They sold Sunagakure's gold and silver jewelry back to Konoha at low prices, then brought Konoha's fabrics and delicacies to the Land of Wind to sell.
Ordinary horses could not remotely match a shinobi's speed. Add a marvel like a Sealing Scroll, and even an average shinobi could carry a considerable quantity of merchandise to trade.
With such exceptional advantages, every last person in the business made a fortune.
Over time, more and more people entered this lucrative industry.
These shinobi, originally responsible only for transporting supplies, banded together in small groups to sell their goods more effectively. Gradually, they formed an organization, building roads, maintaining security, and providing food and lodging.
Some even rode exceedingly rare giant summoning beasts, parading through towns and traveling from place to place, all so they could carry more goods and make more money!
Like red blood cells in the bloodstream, these Courier Shinobi