One reason why junk calories are cheaper than healthy ones, why highly processed foods can cost less than fruit and vegetables - NY Times article You Are What You Grow here (wonder if it's the same reason here in Oz? Hmmmmm).
Be interesting to know the environmental impact of highly processed vs fruit and veg.
After the brilliant TV series, Jamie's School Dinners, about food in UK schools, it's unnerving to read that subsidised food programs in the US are promoting junk food ahead of healthy food. Which means on two counts that the opportunity to effect change is within the power of government.
From memory, you have to register (it's free) to read NY Times material online.
PS. The school canteen with which I'm best acquainted has completely revamped its offerings, in line with the NSW Healthy School Canteen Strategy. The profits from the canteen go towards the school's operations, via the Parents & Citizens Association, which runs the canteen. Over a year after the revamping, it is doing well - the managers have done remarkable work, and the new menu has been embraced by the student clientele. So dumping unhealthier foods for healthier (often, but not always, less processed ones) has paid off in more than one way.