By the way, just to give an estimate on the value of gold in the game since the anime decide to cut it(and the value of gold depend on how much gold is in circulation), an average level 90 player will have between 10k to 50k gold. So taking the average of 30k gold each player, buying city of Akiba would require the total gold of around 20 thousands player. If they sell all their item to the NPC(because selling between player will just move the money's possession, not the amount of money itself), around 15 thousands players whole possession might be enough to buy the city of Akiba(basically, everyone's in Akiba would have to become naked and pitch in to buy the city of Akiba
).
This is just rough estimates, just to give some kind of benchmark how expensive the city of Akiba is.