Meta has built its massive data center and computing infrastructure for artificial intelligence projects so quickly that CEO Mark Zuckerberg is even a little surprised.

In a call with analysts Wednesday after Meta's third-quarter earnings report, Zuckerberg explained to investors how Meta's rising costs for the year are related to the speed at which employees can turn on data centers, servers and chips for AI.

“At the beginning of the year, we had a range of what we could potentially achieve, and we were able to achieve more than we had hoped and expected at the beginning of the year,” Zuckerberg said.

It also means investors face higher costs. Meta raised the low end of its 2024 investment forecast to $38 billion from $37 billion. The cap is still $40 billion.

“I’m actually very happy that the team is doing a good job here,” said Zuckerberg. “This implementation makes me a little more optimistic that we can continue to expand this at a good pace.”

Meta added that spending, which includes the billion-dollar purchase of Nvidia's graphics processors, will increase significantly in 2025.

Meta shares fell in extended trading on Wednesday even as the company beat earnings and revenue. Part of the concern was weaker-than-expected user growth and rising costs.

On the earnings call, Barclays analyst Ross Sandler asked Zuckerberg how quickly Meta can build the massive computing infrastructure required, given potential obstacles such as power requirements and the time it takes to develop its own custom AI-specific chips to achieve its goals around generative AI.

Zuckerberg responded by complimenting Meta's infrastructure team, which he said is “doing a pretty good job” of building more computing capacity for various AI projects such as the Llama family of large language models.

Wall Street is increasingly concerned that tech giants like Meta and alphabet spend too much on infrastructure without generating immediate returns. This is an issue that Zuckerberg acknowledged in an interview with Bloomberg in July, telling Emily Chang that there is a possibility that companies are “overbuilding now.” However, the risks of underinvestment are too great, he said.

“The formula around building out infrastructure may not be what investors want to hear in the near future that we're building out,” Zuckerberg said Wednesday. “But I just think the opportunities here are really great. We will continue to invest significantly in this matter and I am proud of the teams who are doing a great job of providing a large amount of capacity so that we can deliver best-in-class models and best-in-class products.”

This is not the only place where investors have to accept high expenses.

Meta's Reality Labs unit, home of Metaverse technologies, posted an operating loss of $4.4 billion in the third quarter. The company said it expects “operating losses to increase significantly in 2024 compared to the prior year due to our ongoing product development efforts and investments to further scale our ecosystem.”

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