Depending on the time you are going, it is more expensive during peak season.
For your information, we spent about HK$70,000 for a trip of two weeks covering Czech and eastern Germany two years ago during summer holiday for 2 adults and 1 kid. Air tickets is the major expense because we took CX (there are many other cheaper alternatives). Hotel about HK$1,000 per night (one room for all of us). We took public transport such as train and bus. Daily expense on food and other essential items is about HK$1,000.