I have two mini foxies, which cost me approx $7 a week in total to feed.
I feed them mince of either - veal, chicken, roo, kidney, lamb from pet supply places, which costs anywhere between $2 to $3.50 per kg. This is mixed with plain rice and veges (sometime frozen) like carrot, corn, peas, celery, broccoli, etc.
I also buy them kibble - I was buying Royal Canin, but of late have been giving them Pal kibble for small dogs (good little bite size pieces). I feel that they are getting enough with the mince, rice and veges that the kibble is like a side portion rather than meal in itself and so cannot justify the price of the more expensive kibble.
I also give chicken neck, wings about 1-2 times a week.
Very inexpensive, but I guess they are small dogs. Surprises me when people say that their pets are expensive to feed (unless they are large dogs).