I live cheap. I eat decent. I'm really only lacking on fresh produce. And maybe red meat. And as a busy full time student/full time employ who lifts and does numerous endurance athletics, meal preperation time and cost is very important.
$4.50 - 5 dozen eggs. I eat up to 12/day. Lasts about a week. 6g protien per.
$.50 - can of lowgrade tuna. I eat 3-6 per day. 33g protien per can.
$1.58 - 1 loaf of Granny's Delight Whole Grain Fiber Bread. A very healthy bread with each slice containing 6g fiber. Very important. I eat 4-8 slices a day.
$4.70 - 10 pound bag of chicken quarters. If I'm short on time I'll just through them in a pot and boil them. Takes about ten minutes to de-skin and the just wait. Lasts about 2 days.
$.70/pound - Whole chicken (about $2.50-4.00). Just pull the skin off and throw it in the oven at your preference. Sometimes I'll do 200F for 6-8 hours or 375F for 1-2 hours.
$1.50 - 1 pound bag of frozen stirfry veggies. Add some chicken if you want.
On the weekends I'll buy redmeat. Usually something cheap ($1.50-$2.50 per pound).
Also smoothies are cheap. Just throw some ice, yogurt, a banana (or strawberries or whatever), and some all natural peanut butter in the blender and viola! It's cheap ($1.00?), easy, healthy, and fills you up for a while.
OF course, if you don't have any dietary needs (no weightlifting, or slow metabolism, or care about health, etc...)you can live cheaper on roman noodles, PbJ, chefboyardee, etc...
$100 may be pushing eat. $150 is more realistic.