It's just fresh vegetables, every fastfood joint has to transport and store some fresh vegetables, if nothing else they need tomatos for the deluxe sandwiches. Most of the non-burger fastfood joints (like Subway) get a delivery of stuff every day (burger joints usually get by on two deliveries a week, one that has everything and one that's just refrigerated goods). The reason the all healthy food fastfood joint will never be invented is there's no market for it, there's just not that many people hooked on healthy food and the ones that are look down their nose at fastfood and wouldn't go there anyway.
Thse deliveries add up. The difference between making one giant delivery a month (frozen burgers, buns, etc) and two giant deliveries a week (fresh veggies, fruits, etc) is huge. Also, fruits and veggies go bad. There's a lot of spoilage.
I recently ate at a fast food health food store (independent). I had a salad, "health shake" and something that looked like ice cream. The total was close to $20. That's more than double the average fast food franchise purchase.