While most high-cost U.S. cities dither over building new housing for their surging populations, the government of Hong Kong is considering building new land.

Last week Bloomberg covered Hong Kong Chief Executive Carrie Lam's proposal to build four artificial islands—whose total size would be about one-fifth the size of Manhattan—on which new as many as 400,000 units of new housing could be built, providing homes for up to 1.1 million people.

"The shortage of land supply not only leads to a shortage of housing supply, but also affects people's quality of life," said Lam during an October policy address to the Hong Kong Legislative Council, when she first endorsed the idea.

The idea for new land as a solution to the island's high housing prices—the highest of any city in the entire world—is an interesting one, and it's hard not to get excited about literally raising islands from the sea.

Nevertheless, there are a lot of reasons to think that this land reclamation scheme is a giant boondoggle, the goals for which could be just as easily achieved through the kind of zoning reform cities are normally loathe to embrace.

For starters, Lam's new islands would not come cheap.

The Our Hong Kong Foundation—which first released a detailed policy proposal for building the new islands in August 2018—put the cost at HK $1,360 per square foot of reclaimed land which works out to be about $32 billion in U.S. dollars, or roughly 10 percent of Hong Kong's GDP. One government source told the South China Morning Post that the land reclamation plan would cost up to $68 billion, while an environmentalist group has pegged the costs at closer to $128 billion. The government of Hong Kong, a self-governing "special administrative region" of China, has not released official estimates.

That's a lot of money however you slice it, which only further frustrates those who say the project's aspirational completion date of 2032 won't address the region's immediate and pressing problem of housing affordability.

There are things the Hong Kong government could do right away to help reduce the city's astronomical housing costs, including reforming zoning in the territory so that more housing can be built on land that already exists. A large majority of land that falls under Hong Kong's jurisdiction is actually zoned for "green space"—meaning parks, reservoirs, and farmland—and is thus ineligible for housing.

Rezoning this green space could open up a lot of new land to development, but it would be incredibly controversial. Much of what has been zoned "greenfield land" has been snatched up by private developers waiting for the government to rezone the land, which would set them up for a tidy profit. That might not matter to libertarians, but in Hong Kong—where developers are not incredibly popular, and where government-funded public housing is the norm—it's politically dangerous.

Making matters worse is that even in areas where land has been rezoned to allow for new residential development, the Hong Kong government has shot down many proposed projects, or imposed building requirements that make these projects infeasible.

So while building new land is an undeniably cool idea, it's also not the most practical one. The most practical solution to a housing shortage is far more boring, as well as cheaper and faster.