Neom's planners are reportedly worried people won't want to live at the bottom of a 1,640-foot horizontal skyscraper

• Neom planners are worried about The Line as costs skyrocket, The Wall Street Journal reported.
• Planners are reportedly concerned the horizontal skyscraper's design might not appeal to some people.
• The first 1.5 miles of the megaproject could cost more than $100 billion.

The cost of Saudi Arabia's Neom project seems to be spiraling — and that's not the only issue concerning planners.

According to The Wall Street Journal, they're concerned that The Line's vertical city concept will not appeal to some potential residents, given the levels of natural light likely to reach the lower levels of the parallel structures.

They will be about 1,640 feet high — not far off the World Trade Center in New York City, which is 1,776 feet. According to Neom's website, the city will have no roads or vehicles and run entirely on renewable energy.

Some have already raised questions about The Line's design.

Leonard Chan, chair of the Hong Kong Innovative Technology Development Association, cast doubt on the city's practicality after attending Neom's roadshow in China last month.

"I'll visit for fun, but I won't live there. It's like something out of SimCity," he told news agency AFP.

Another attendee, Plato Yip, chair of the environmental group Friends of the Earth in Hong Kong, told the outlet he worried the city would feel isolated. The concept of the mirrored city "feels like being caged inside, even though it may be very comfortable," he added.

Even architects working on The Line have questioned the feasibility of the project.

Last year, British architect Peter Cook, who is involved in the project, called the city an "amazing absurdity," adding that the proposed height was "a bit stupid and unreasonable" in comments reported by the Architects Journal.

The cost of Neom could also prove to be an issue.

Saudi Arabia's official estimate for the project is $500 billion, but recent reports have claimed that funding for the futuristic megacity could skyrocket to more than $1.5 trillion.

According to the Journal's report, executives working on Neom have dismissed the $500 billion figure as unrealistically low. The first 1.5 miles of The Line alone is expected to cost more than $100 billion, two unnamed sources told the newspaper.

Neom employees expect the true cost of the mirrored city to be more than $2 trillion, per the Journal.

Saudi Arabia has been trying to counter reports that the project has suffered recent setbacks. Last month, the Saudi economy minister told CNBC there was "no change in scale."

This week senior Saudi officials were withdrawn from the Milken conference in Los Angeles to brief Saudi Crown Prince Mohammed bin Salman on the progress of Neom, Semafor reported.

Representatives for Neom declined to comment.