About 25 ounces of gold per kilogram of gold, at 12 troy ounces per pound.
3K dollars per ounce = 75k dollars per kilogram of gold.
5K kilograms x 75K dollars =375 million dollars per year at 2.5 Gigawatthours per year.
The article says gold would be a byproduct, not a cost of operation.
All theoretical, of course
A troy ounce is very close to 31.1 grams, so there are about 32.15 troy ounces in a kilogram, not 25.