Q: As there are differences in economies from World to World, will the housing costs differ by World?
A: It will be the same for all Worlds. The land for housing will be an auction system, and will start from a high price and over time will become cheaper.

I have no problem with the auction system because it is a reverse auction system. If the land sits on the auction house for days, the price will gradually begin to fall. So it won't be going over the price, it will be going under. Now, you may not see super cheap land for housing at first, but over time once people buy their land you could see it more often.