If your idea of wealth is only determined by currency then building an objective difference in wealth is quite simple but a person can be holding a briefcase of millions of dollars in the middle of the desert and his wealth has no value. That value is subjective. The arrows in your example may not have a range of quality but that doesn't mean the arrows would not have subjective value to different players based what those players need and what they can spend to achieve those arrows. Much like the person with briefcase, I bet after a day in the desert with nothing else they'd be happy to give up that entire briefcase for water. A player with lots of gold to spend and not enough arrows will spend the money to get arrows because they feel they need them.
Your inkling about societies seems to be pretty historically sound since nothing lasts forever (possibly energy, but black holes muddy that water, as far as my understanding of physics goes).
Value exist because people need things (or are made to think they need things). As for purchasing options, a wealthier nation simply needs more options to waste resources on to uphold its ruse of wealth. The true measure of wealth is subjective. Wealth is by definition the abundance of valuable resources or material possessions and as my example pointed out, money has no value unless someone else needs (or thinks they need) it.
When Africa was colonized its potential to increase it's quality of life along side other nations was lost to slavery, civil war and stagnating traditions causing cultural stagnation do to the lack of access to the necessities of life. When you're country is trying to join the global market, it's hard to win any ground when the wealth of your nation belongs to foreign interests. This is the fate of the middle east since its easy to buy a nation that can't afford to fight itself.
As for you're tangent. I'd like to see games that explore the fall of corporate empires as well. It'll be refreshing to join Star Citizen since it's story seems to be based during the decline of an empire.