City funding has been pivotal to the development of Hudson Yards, Blau added—and even that has been used creatively. "What's never been done in NY is TIF [tax increment financing]. We received city issued bonds under the Hudson Yards Corp. and New York agreed to pay for the 7 train extension to the site, so we were able to get that done without taking any bite out of the MTA capital budget."

For Silverstein, the World Trade Center's mixed ownership was helpful with financing the project. "The World Trade Center is the epitome of a public/private partnership," noted Burger. "The Port Authority of New York & New Jersey owns the land, so we coordinate with the state governments and we don't have to pay taxes. We also don't pay commercial rent tax, so tenants get that benefit, and we don't have a sales tax on FF&E."

Added Kushner, "What we did in the Watchtower buildings is subsidize rents. We said we'll get about $120 per square foot and we'll take $60 to $70 to get the retail tenants we want. We needed to do place-making to make the space attractive."

Still, creating such projects isn't easy, largely because their scale requires a long timeline. "The models we put together are based on science but they're fiction," Kushner asserted.

"Knowing you're going to go into a project that will take 10 to 15 years, everything possible is going to happen in that time," explained Blau. "You need capital flexibility and to make sure you're not stuck with unrealistic construction deadlines. It's about constantly making sure you're prepared for the unexpected."