To add to what Fizzle mentioned about the food, just to clarify, the reason its recommended to NOT give piggies food with all those bits isn't because they don't need them and its cheaper to give only pellets (which isn't the case) but because the bits aren't healthy for the piggies. They're more or less junk food which can lead to picky piggies not eating the pellets which contain the required nutrients leading to malnutrition (put candy and veggie's on a kid's plate, which are they going to eat?). They're also not intended to eat seeds and the shells can get stuck in their throat.
Additionally, brands with the bits (probably Kaytee or something similar) are not always very high quality even in the pellet department (cheap by products and filler and and some brands use preservatives which are banned in human food but can still be used in animal food despite being possible carcinogens- I've seen some brands using chemicals otherwise used as pesticides as preservatives in their pellets). Oxbow pellets are safe, use quality ingredients and are balanced for nutrition.