Just throwing stuff at the wall here, but with the coming population collapse, I'm thinking we might be able to derive some lessons or maybe even a blueprint for how to navigate said collapse by examining MMORPG economies. I know that in the past economists have studied WoW in earnest so maybe there's still some insights yet to be mined.
How does the economy change once the server population starts shrinking?
I know from my own experience playing FFXI back in the early 2010s that there were regularly specialized materials on the auction house that wouldn't get stocked regularly. In my case it was some fish and for a couple weeks I was able to make good money at it because while there was almost no one supplying the item there was definitely still a demand for it. Then someone started flooding the market and I moved on to other ventures. No idea if the end result of that was a temporary supply or if it turned into a stable availability of the product. Maybe the one guy just made a whole bunch of product the one time and then once it was sold he moved on to the next thing and all the smaller producers like me ended up gone and the product itself just outright vanished from the market.
I imagine the dynamic is quite different now as the population dwindles further, although they do consolidate servers so that might throw a wrench in the fact finding opportunities here.
Having played HC for some years I'll add the only real limit the devs imposed on farmers was having no more than 3 characters logged in at a time. Players could easily manage this by running multiple clients at once and barring special circumstances like open world raids, where players were usually limited to just 1 character/account unless on a low pop server that wouldn't reach the 50 player zone cap, the only thing stopping anyone from running 3 farmers at the same time was their own motivation and time to organise it all. Plus the point doing so meant they couldn't then actually play the game at the same time due to the 3 character limit.
Still, it was extremely helpful having farmers dumping so much into the economy because they not only earned the item drops but also generated currency while doing it. The AH would always take a cut which removed currency from the game. So those who "made" money through flipping and reselling were really only redistributing currency while also removing some per transaction. Farmers on the other hand would often generate so much they'd spend just as much on things they wanted because they had millions, if not billions, and didn't care how much they spent, so sometimes poorer players would get far more for their sale than expected.
Also at times sometimes people fucked up and put an extra 0 or even a 9, which is how I had items I usually sold for 10 mil sometimes earning me 100 mil if not more.