Lunch:
In the office: ~ $25 (bring from home almost every day)
On the road: ~ $40 (bring if possible or salads)

Dinner:
Home: ~$40-60 (cook most nights, so $$ is for groceries, wine)
On the road: ~$30-40

I try to eat as cheap as possible on the road, as our per diem is $50/day for food, and we keep what we don't spend.