Typically I would expect a restaurant lunch in a major city in the US to cost $20-$40 per person after taxes and tip.[1] So, essentially $5,000 - $10,000/year. This was for people with salaries running from about $50,000 - $200,000 before income tax, so something like 7% - 20% of their after-tax income.

Making a lunch and bringing it instead should be less than half of that, especially if one makes extra food for dinner and brings the leftovers for lunch the next day, but I guess a lot of people actively dislike cooking for themselves.

A decent amount of tech workers also get dinner at restaurants nearly every day, which is of course even more expensive.

[1] Excluding inexpensive franchises like McDonald's, Burger King, Wendy's, because my coworkers typically did not get lunch at places like that.

Compared to everywhere else, Americans make more.