Why does housing initially need to be a massive gil sink?
Housing should be something that is attainable by the majority of players. Its fine if there is small goal to attain. But the prices should not be in the high millions of gil. The reason for this is that the majority should have access to benefits such as chocobo raising or gardening.
I'm completely fine with upgrades to houses being costly. Create a system where certain room add-ons (not furniture) or other benefits are a really high cost if you must.
As a paying subscriber, I do not care if your servers "cannot handle the load". That is no excuse to limit housing to the top 1%. In other words, the technical limitations of the game should never be a massive impediment to enjoying content. That is your problem to figure out, don't make it mine.
Fix this.