cr:5.1.6a

First, rules define the starting asset-cost. Second, effects that set an asset-cost are applied. Third, effects that increase an asset-cost are applied. Fourth and finally, effects that reduce an asset-cost are applied - if an effect would reduce an asset-cost to be less than zero, it instead reduces it to zero. If two or more effects are applied at each step, then they are applied in timestamp order.[6.3.4]