Building project cost overruns are not unusual
Rising estimates for the West Kowloon Cultural District should not cause alarm

In the mid-1980s, I participated in the feasibility study for the Three Gorges hydropower project on the mainland. At that time, the total cost of the project was estimated to be around 80 billion yuan (HK$100.4 billion).
It was based on a preliminary design of the 2.2 kilometre-long dam, and preliminary estimates of the costs associated with resettling the population affected as well as with the protection of historic sites and the environment.
By the time the final design of the dam was completed in 1993, the updated total project cost was 200 billion yuan. Approximately half of this was resettlement cost. Between the mid-1980s and 1993, the number of people that needed to be relocated rose from about a million to more than 1.2 million, and the cost of resettlement went up accordingly.
In addition to compensation in cash, many new towns had to be constructed to accommodate the population affected, along with schools, hospitals, community centres, etc.
The cost of preserving historic sites also went up significantly.
In addition to a huge amount of archaeological digging and the relocation of temples and other historic monuments, an "underwater" museum was built to preserve historic records of low water levels since the Tang Dynasty, as recorded on rock and carvings on a sandstone island in the middle of the Yangtze River near Fuling district, Chongqing . That museum project alone cost about 200 million yuan. All these costs could not have been accurately estimated during the feasibility study in the mid-1980s.