There are going to be regional differences of course, but here in SF, a modest lunch costs at least $20. My average was around $25, or about $6500/year.
I adopted "meal prep Sundays" where I make all of my lunches for the week ahead, and the average cost is consistently around $5, making my annual weekday lunch cost about $1300. +$5200/year post tax to be used on other things.
Applying the same general idea to dinner unlocks further savings.
The funny thing is - I don't know that I'm even sacrificing time with this approach either. It takes me maybe 1.5 hours on Sunday for the lunch prep thing, but I'm saving a bunch of time by not physically going to restaurants, ordering, taking deliveries, etc. The variety is lacking with this approach, but the tradeoff is well worth it in my book.