Elon Musk said Sunday that free staff lunches at Twitter's San Francisco headquarters cost over $400 per meal because 'almost no one' was in the office. 

The billionaire said that according to badge-in records, average occupancy in the office over the last 12 months was below 10%, peaking at 25%.

Musk tweeted Sunday after The New York Times reported that Twitter employees would have to start paying for office lunches themselves.

He said criticism of the move was "especially bizarre given that almost no one came into the office," adding: "There are more people preparing breakfast than eating breakfast. They don't even bother serving dinner, because there is no one in the building."

Musk said that Twitter spends $13 million a year on food service at its San Francisco HQ.

Musk was slammed on his $400 meal cost estimate by Tracy Hawkins, a former Twitter employee. Hawkins' LinkedIn profile says she was a VP for real estate and work transformation at Twitter, focusing on hybrid working.

Hawkins said of Musk's estimate: "This is a lie. I ran this program up until a week ago when I resigned because I didn't want to work for @elonmusk.

"For breakfast & lunch we spent $20-$25 a day per person. This enabled employees to work thru lunchtime & mtgs. Attendance was anything from 20-50% in the offices."

Musk said Hawkins' figures were "false."

The contradictory figures could be because Hawkins referred to "attendance" across multiple offices, while Musk spoke about occupancy rates at Twitter's San Francisco HQ specifically.

In an interview ahead of the G20 summit in Indonesia, Musk said he was working from "morning to night, seven days a week," adding: "The amount that I torture myself is next level."