Ever think that maybe buying the better helmet only gets you a more comfortable fitting product and just might be the low safety standard rather than the department store helmet?

Expanded polystyrene foam (aka "Styrofoam") is expanded polystyrene foam. I manufacture foams. There wouldn't be a performance difference in the material itself because it's all polystyrene foam. The more expensive ones for more venting actually have less foam, thus less energy absorbtion than the cheap helmets with less venting thus more foam.