The royalty agreement provides for a minimum obligation to be paid in monthly payments over a total of 400,000 ounces of gold, or 4,167 ounces per month over an initial eight year period. As of September 30, 2010, payments had been made on a total of 70,764 ounces of gold with further payments to be made on an additional 329,236 ounces of gold
you do the math
329236 ounces Gold x $1300 = $428,006,800