I am going bk too , 12-23 to 01-13, 我係台灣人no need hotel, 台北西門釘有D 旅社 very cheap around $ 800 TWD per nt,又近shopping and eat , take 飛狗bus from airport to 市區...I think hotel around $ 2500 or more depends,
tkt my grandma bought from 華航on special
around $ 1500 HKD per person, Anyways,
I think 6000-10000 HKD is enough for this trip, but really depends how you spend,
hope it helps u