Monopolize, even if it could only be circulated within a city, was enough for the ruler to control well.
Therefore, the foundation of Black Rock City was actually hegemony. They relied on force to provide security within Black Rock City, and then used high prices to harvest the wealth of ordinary people.
Correspondingly, Black Rock City could dominate the place, but it wouldn't work on outsiders. Even if they were merchants, foreign chambers of commerce wouldn't buy black rock coins. Even if they did, they would exchange them for goods before leaving.
However, this did not affect the enjoyment of the upper echelons of Black Rock City. To them, it was something that could allow them to enjoy glory and wealth for generations.
Now that they had everything they needed, they would naturally look for something that was scarce in Black Rock City to differentiate themselves from ordinary people and obtain a greater sense of superiority and satisfaction.