Hm.... From health class a long (well, long for me) time ago can't you sustain yourself with more like 1500 calories? Especially if dealing with a smallish, sedentary, techie-type?
Well, it depends on things like age, gender, size, and activity level.
According to DietOrganizer v1.3, here are some caloric requirements to maintain current weight, based on a sedentary lifestyle:
22-year-old male, 5'6" tall, 155 pounds: 1865 calories/day
25 y.o. male, 5'7", 180 lbs: 2276 calories/day
25 y.o. female, 5'7", 160 lbs: 1879 calories/day
30 y.o. male, 5'10", 180 lbs: 2281 calories/day
30 y.o. male, 6', 220 lbs: 2615 calories/day
40 y.o. female, 5'11", 200 lbs: 2365 calories/day
Most of the nutrition charts on food labels, when calculating percentages of daily nutrients, assume an average of 2000 calories/day.
I poked around to see what body sizes would maintain at 1500 cal/day, with a sedentary lifestyle. It's possible, but all (healthy) results I came up with involved either the elderly, or very very small or thin people:
60 y.o. female, 5'8, 125 lbs
20 y.o. female, 5', 95 lbs
30 y.o. male, 5', 98 lbs
So yes, you're right, 1500 cal/day would probably keep you alive, but it's generally used more as a quantity designed to help lose weight. The target of my calculations has been based on maintaining current weight, but it really all depends what you're aiming for!
RE: Lunch for about $1 a day: BumbleBee Tuna