I went through about 13.6kg/30lbs of candy. Made a bit of a camp fire front of the house, a bit of hot chocolate, and all was good.
We had left overs last year, and didn't buy enough this year. My neighbor gives out full size candy bars to kids in costumes and unpackaged Brazil Nuts to kids without costumes. I think he spends a couple of hundred dollars easily. One of my wife's Facebook friends is a Doctor and in their neighborhood (over in Seattle) they get over 700 trick or treaters every year. Apparently it's a real nice area and they bus kids in.