I don't think that's really an anti-trust problem, and I don't think you can call a majority of voters in an area a "cartel". It's a matter of giving the majority of residents/voters what they want, even if it's bad for them in the long run.
> I don't think that's really an anti-trust problem
What kind of problem is it then? High prices being maintained by a purposeful conspiracy of existing owners to constrain supply sure sounds a lot like an antitrust problem.
> It's a matter of giving the majority of residents/voters what they want, even if it's bad for them in the long run.
But it's not necessarily bad for them. They make more money by monopolizing the local real estate market in the same way as any other cartel monopolizes anything.
Even if their choices are bad for the city itself, they may be planning to sell and move to another area before the long-term negative consequences to the city are felt.