We expect to employ the world’s leading Quantity Surveying companies who will give us accurate figures all through the D&C process. In addition we will have fully costed Feasibility Studies completed by our Project Management Company and signed off on by one of the big four accountancy companies eg. PWC, Ernst & Young. Until then it is unprofessional for us to provide guess work figures.
However we can reference you to the current costing of similar contemporary developments of new cities as follows:
The cost of building an ultra-modern city from scratch.
Jeddah Economic City (Saudi Arabia) cost $20 billion duration 3 years
https://www.google.com.au/?gfe_rd=cr&ei=DUuYV_qKEMTu8wfl17GIBQ&gws_rd=ssl#q=sky+city+1000
New Songdo City (South Korea) cost $40 billion duration 10 years
https://en.wikipedia.org/wiki/Songdo_International_Business_District
South Korea is building a $40 billion city designed to eliminate the need for cars
Masdar City (Abu Dhabi UAE) cost $20 billion duration 8 years
https://en.wikipedia.org/wiki/Masdar_City
King Abdullah Economic City (Saudi Arabia) cost $86 billion duration 10+ years
https://en.wikipedia.org/wiki/King_Abdullah_Economic_City
X-SEED 4000 (Japan) cost $0.6-1 trillon
https://en.wikipedia.org/wiki/X-Seed_4000
Cost of hosting the Olympic games (including construction costs for athletic facilities, transportation infrastructure, and housing, and operational costs)
Sochi $51 billion
Beijin $46 billion
https://www.aeaweb.org/research/are-the-olympics-ever-worth-it-host-city
NEOM City South Arabia $500 billion