My wife seems to have a more delicate palate than I do. I might get tired of pasta but I can eat it easily a few nights of the week. Pasta is pretty cheap, as is rice. Both can be cooked up ahead of time and put into the fridge. Keeping pasta, rice, shredded cheese and perhaps a few other ingrediants on hand is pretty cheap for making fast meals on the go. Raisens, craisens, and some other dried fruits do have long shelf lives, and can be quickly added to a lunchpail.
Me, I like pasta or rice with some frozen mixed veggies. I used to add butter but these days I just sprinkle some shredded cheapo mozzerella onto it. Or pasta with sauce. I don't always need meat, but a bag of chicken strips that you can microwave, while being somewhat expensive, can last a long time--if you are only using a few strips at a time. We have a small stash of tupperware that works well for meals.
Quesadilla's are good, and fast to make. A bit of salsa can wake 'em up. But those don't do well for taking in the lunch bag to work. My wife found these flaxseed wraps which are both low in calories and really yummy--I look forward to spinach wraps with a bit of ceaser dressing on the weekends for lunch.
I find it hard to get veggies. I like my frozen mixed veggies though, and those are cheap. We do try to keep celery and carrots and cucumbers on hand; but my kids tend to snatch them up before I even remember they are there. The celery and cucumbers don't seem to last long once you peel/cut up either. I can't eat peppers so those are out.
My wife is stay at home. Sorta. She's probably more busy than I, but at least she's home some of the time. During the winter months she will roast a chicken one night, then boil and make stock the following day, and then I have like a month's worth of soups from that. She's nice and will divy it out single portions into the tupperware for me. She likes the Progresso canned soups but I'm coming to dislike those--but her homemade soups are simply not outdone by anything I've ever bought.
My kids like the cheapo chicken nuggets that can be microwaved, or hot dogs. They're growing and so they can eat that stuff.
There are these Thomas multi-grain muffins that are high in fiber and low in calories; I've found I like eating the "light" version straight up, no toasting, nothing on them (or dunking into my soup).
Personally, I like PB&J sandwiches. Kinda caloric, but yummy. Smuckers makes this "low sugar" jelly that, if you read the ingrediants, uses only sugar, not HFCS. I've been on a kick tho lately to cut sugar from my diet, and haven't had PB&J in a while. Found out that I can indeed stomach oatmeal with no sweetner in it; that makes for a decent breakfast, although TBH I prefer a nice toasted bagel.
I'm almost to the point where I'd rather not buy sandwich meat for home, and instead buy "real" sanadwiches when I go out. I mean, I would never pile my sandwich up with meat at home like they do in a real shop.