You can buy frozen veggies
for a fraction of the cost of fresh and they are just as good
for you. Add
a meat, eggs, dairy, etc to get your protein, bread or cereal to get your whole grains a serving or 2 of fruit every day, some healthy fat, such as olive oil, and avocado in your salad.
You can actually buy a head of lettuce, tomato, cucumber and other raw veggies that will make a couple of meals, less expensively than you can buy a ready made salad that will only make one meal.