Photo provided by State Administration of Science, Technology and Industry for National Defense shows the image of the rover for China's Chang'e-4 lunar probe. (Photo/Xinhua)

Recently, CGTN Digital received questions from readers about the cost of China's Chang'e-4 lunar mission.

So how much money did China spend on building the Chang'e-4 lunar lander, the Yutu-2 lunar rover and the rocket to send them to the far side of the Moon?

According to Wu Yanhua, deputy director of the project, the total cost of the mission was "not much."

"The cost is close to building one kilometer of subway," he said in a press conference back in January 2019.

The cost-per-kilometer of subway in China varies from 500 million yuan (about 72.6 million U.S. dollars) to 1.2 billion yuan (about 172.4 million U.S. dollars), based on the difficulty of construction.

So we still don't have the exact number, but the range is close enough to give people a solid estimation of the cost of a Moon trip.

By comparison, India's ongoing Chandrayaan-2 mission has already cost about 141 million U.S. dollars.

Is the Chang'e-4 really "reused trash?"

Wu also revealed another detail that Chang'e-4 was not designed to go to the far side of the Moon initially.

"The Chang'e-4 lunar lander was originally a backup to the previous model Chang'e-3," he said.

Since the Chang'e-3 was a success and no longer need a backup, the Chang'e-4 was "re-purposed for its current mission."

Wu didn't directly say the move saved money for China's space program, but it's obviously true since the Chang'e-4 recycled material from an already successful mission.

"The Chinese government's investment in the space program is in parallel with the country's economic situation," he concluded.