What is the standard of review applicable to a discretionary costs order?

The proper standard of review applicable to a discretionary costs order was set out by Cameron J.A. in Benson v. Benson (1994), 1994 CanLII 4554 (SK CA), 120 Sask. R. 17 at paras. 89-90: … In general costs are in the discretion of the court with full power to determine by whom and to what extent they are to be paid. The exercise of that discretion has been taken to be limited only by the need to act judicially on the facts of the case. Its exercise is otherwise "unfettered and untrammelled"… That, combined with the nature of our function in relation to appeals concerning the exercise of judicial discretion, serves to significantly narrow the scope for appeal. The discretion is vested in the trial judge, not us. And our function, at least at the outset, is one of review only, review for error vitiating the exercise by the judge of that discretion. The obvious aside, vitiating error is to be found either in misapplication of some governing principle or rule or in disregard of some critical fact or other consideration. Either that or it is to be assumed in the case of an order so obviously unjust as to invite intervention. But in the absence of something of that sort we are not to wade in, substituting our discretion for that of the trial judge.