A market achieves equilibrium at a price point where supply equals demand.
If the price point is artificially kept lower than the equilibrium point, the result is a shortage.
If the price point is artificially kept higher than the equilibrium point, the result is a surplus.
Supply is the same for all servers.
Demand is different for each server, thus resulting in a different equilibrium point for each server. Past pricing models seemed to make an effort to account for this, either to reduce demand or to reduce the supply of Gil on certain servers (housing takes Gil out of circulation).
As to why they do it differently now, I don't know. The only way to make everyone happy is to have a limitless supply of housing, which they've said they can't do.
Some things they could do...
1. Give more housing to servers with more population.
2. As a compromise of sorts between the two camps in this argument, they could have wards at multiple price points. For example, the first set of wards could be 3 mil for a small house. Second tier is 5 mil. Third tier is 10 mil. The cheaper ones of course sell out faster and give people with less Gil a chance to get in. Expensive wards would not sell out overnight so housing wouldn't only be available during the Walmart Black Friday bum rush.
The economist in me would advocate a system wherein market forces can determine equilibrium, such as an auction system or one where initial prices were stupid high and came down over time until buyers are found (not unlike the current system, but with higher starting points and lower ending points).