I'm sure a lot of people know this, but I'm also sure quite a few people don't. So I thought I'd explain the idea of deflation due to a reduction in the money supply and how it will probably affect the economy over the next few months. Hope it helps you make an informed decision! :]

Tempted to buy a house under the new system?
Is your FC about to spend 300-600mil?
HOLD ON A MINUTE! By saving your gil, you could become even richer!

With extreme prices, the goal of the housing market is to act as a "gil sink"
Essentially, this is a mechanism that removes gil from the game economy

Imagine that the game economy had 100million gil, split up between everyone
And suddenly, 50mil of that 100mil disappeared
What would happen?

This is called money supply in economics
And monetarists argue that reducing the money supply leads to deflation

What is deflation? It's a general decrease in the price level of goods and services.

So what does this mean for you?
If lots of FCs blow 100s of mils of gil on housing, the money supply in eorzea falls
If money supply falls, people are less willing to pay large amounts of money
So prices for everything drop!

Let's take a relevant example:
in 1.0 all gil was cut to 1/10th of its value. if you had 100mil before 2.0, you ended up with 10mil in 2.0.
What happened? Prices dropped. A LOT. In the first week or two people were still paying huge amounts of gil for items (1.0 prices). But these quickly plummeted, resulting in very few items selling for under 2mil on legacy servers.

So what will happen now?
With 100's of mils disappearing, prices will in general drop
So what's the smartest thing to do in this situation?
Not give away your 300-600mil.
Why?
Because a month from now it may buy you TWICE as much or more.
While you still may only have 300-600mil, its real value will have increased, as it will be able to purchase considerably more items.

So ask yourself which you would choose
Lose 300mil and get a house
Keep 300mil and in a month or 2 have it be worth twice as much (e.g. get 300mil free)

Put another way, the cost of a house isn't it's listed price. You need to take into consideration the opportunity cost (the amount of extra value you are losing by spending your 300mil now)
So the cost of a house may be double what you are actually seeing (in real terms)

This also means once you spend your 100s of mil, it will be -a lot- harder to make that gil back, as selling items on the AH will net you considerably less.

If you don't absolutely need a house, saving your money while others spend theirs can make you and your FC filthy rich! And since housing prices are supposed to go down, you can always get a new house months down the road, at a much cheaper absolute price.