This is not aimed at OP whose point I agree with
I honestly think the issue isn't the supply/demand of houses, it is the inconsistency of players and their back story.
Right now there must be at least 50 properties for sale on the server, but people don't want to buy them. So the issue is not Supply Demand overall, it is localised supply and this is driving the problem (interestingly 18 months ago you couldn't sell a property in Sandy for what you paid for it)
For some reason people would rather spend 500k in a bad area of town rather than 325k for a stunning apartment. It just doesn't make sense
If real life if someone had the money they would 90% of the time choose a better place to live
The next argument will be I want to rp the character in this location. Fine, then create a financial story that supports this. Everyitme people work thier way to hundreds of thousands of cash in the bank and then live a downmarket lifestyle you break the game economics. It's actually called Gentrification and is a real problem in a lot of cities. People sweep up under priced properties in "cool" cheaper locations and within a matter of years the whole area triples or more in price. Hells Kitchen in New York or Shoreditch in London are good examples
If you are that person who arrives in that area and pays max value you are the problem and you are the one driving the prices up, not the seller. If you run a street gang maybe do more checking on characters joining to make sure their finances match their story (/charity is a good command)
What's my point? Until people stop taking advantage of the game economics to amass huge wealth and live in area that are inconsistent with this wealth this problem will remain, no matter how many controls admin apply. It's a community issue, not a rules issue.