Midget boy,
I am quite aware of what current real estate prices are in YVR. They are definitely higher in Sydney than YVR for a reasonable area. Perhaps Melbourne is slightly cheaper, I am not sure, I don't follow current prices there that closely.
I am not sure how old you are but you are looking at it through rose tinted glasses. Is 700sq ft in Tung Chung the gross or net size? That would be manageable for you, and maybe a girlie, but I hope you don't plan on having a kid any time before you would be an FO, because 1) you won't have the room and 2)you won't be able to afford it.
Remember also if you do decide to come here and get jack of your living conditions after 5 years, you will have a P2X type rating that isn't recognised anywhere, and S/O time in your log book that isn't worth the paper it is written on.