alt Hacker NewsI'd say more commonly we say consequence, but I think you can fairly use cost and consequence interchangeably here. They have similar meaning. However, consequence/cost too are subjective. Thus risk is also subjective. Something cannot be objective if its variables are subjective.
Costs are tangible, making them objective, even if they have underlying subjectivities. The cost of milk is objective, even if your purchasing habits are subjective.