Stevo,
I have never really worked it out. The mixed corn is about £8 a bag, as are the oats, meal worms £7 a bag sunflower seeds, peas millet etc £16 for 20kg.
All these are mixed together and last a while, except the oats, which are given during the summer, and they love the soaked oats, the sugars are all released, even over a week old smelly they prefer it to other stuff. A bag lasts me ages. Keeper E looks like he feeds much the same.
Anyone could also feed the same to any bird. Keeps em in tip top condition.
Atb