Any new significant city will need billions if not tens of billions of dollars on transport links, water, sewer, etc, if there is even a way to bring a city sized amount of potable water.
And then you have to convince people to actually move their residences and jobs there. Most people don‘t like betting uprooting their whole family and social lives on a total unknown. History is littered of examples of new failed cities that in the best case scenario became really far bedroom communities, or in the worst case didn‘t get off the ground.