If you have a Big FC and they all chip in 200k (300 players in a FC for instance). You will have 60,000,000 Gil and on my server that would get us at most a First class Small House. If We wanted a Big house first class 625mill Each of the 300 players would need to chip in, roughly 2.1 million ( if most players in the guild even has that much.)

Although I don't agree with these prices, if your FC works hard for it, you can def. achieve that mark. ( 625mil is still outrageous though >.>)