When late-game currency becomes obsolete, it usually just means the town's running those currencies did not do a good job managing their currencies. On the servers I play on, players make a careful note of who the late-game industry leaders are. You have to make sure you are saving up the specific currency those towns operate in so that you can actually afford items they are producing. You do this both by selling them items they are actively buying in their stores, and by listing your own goods in their currency. These players are normally focused on mining high value ores like copper and gold, so they honestly appreciate it when you list more basic things that they need but don't want to divert their efforts to farm; things like limestone/quicklime, logs/charcoal, cooked food, asphalt roads, etc. And often you can do these things cheaper than they can. Because while they are saving stars for end game skills, you can afford stars in things like +1 quicklime, or +1 charcoal Or in the case of asphalt roads, they can't make them at all without the skill. I just finished a cycle where it was clear that only one town was going to achieve mass production for electronics and industry items. I intentionally saved up their currency, and as a result, I was one of the only people on the server who was able to buy every end-game item I wanted, including a truck, a bunch of T5 building materials, and eventually my very own skid steer. Having the skid steer made it that much easier to keep earning their currency, because I was able to rapidly collect and sell them high value ores. Meanwhile, other people kept trading in dead currencies and just sat there complaining (and eventually quit) when they ended up with 10k in cash but there was nothing to spend it on.
essentialy late game money are useless almost. U need them to more useful and u can do that by encouraging the player to build more which is a different activity from just producing and exchange stuffs with other player. Late game the activity of building go missing and so money become much less important. Important only to destroy the asteroid.
I dont think this game need any more greedy owners, plus you can help city go get more lent or exclusive right to use land elsewhere. Infinite profession scaling should hep with this, but its true that the game does not have infinite amount of tiers of building materials and stuff to buy, so sooner or later you run out of need to horde currency