Usually I do cafeteria food. Costs about the same as fast food for as much as I eat($7-8 is normal).
When I was working 0600-1400, I took a box of granola cars in my bag, eat 3-4 of them over the day, and stuff myself when I got home to cheap food. Wendy's a 3min drive away from work, or a full meal for the same price as a burger when I get home... hmm... Still treated myself to a burger every few weeks.
Spent 8 months in school, eating cafeteria food 75-80% of the time. But that's a wrap or sandwich and a bowl of soup at least 1/2 the time. When I wasn't in the cafeteria I was usually up in the lab working on a project or lab that had to get done. Allowed coffee in there but no food at the stations. Many a day fueled on coffee alone.
Spent the last month since I finished that packing on 10lbs getting up at noon and sitting around watching TV and eating till the sun comes up again. Get back to the work world in a week, 0800-1630hrs, and you can bet I'm going back to fruit juice and granola for a month or so, lose the 20lbs I packed on since I worked last(aug 05). So if you call that a lunch, yes I pack my own.
edit:
as far as that "clean your plate" mentality, there's a reason we don't dish up food before it hits the table... just take what you want from the pots. No reason to fill your plate if all you want is a salad for supper.
My grandmother used to make us eat everything on the plate, and keep bringing food till you were stuffed. The only thing that taught me was just how much food I can pack away. Buffets hated seeing our work group, we'd all do 4-5 plates for lunch. We would eat til we were full, not just satisfied.
it's quite suprising how far apart the line is between satisfied and full. I'm satisfied on a 1200 calorie day. Doesn't mean I can't pack away 4000 if I want to, I just don't need to.