For projects with real scope (custom homes, whole-home remodels, kitchens, primary suites), yes. The designer’s value comes from three places: avoiding expensive mistakes (specifying the wrong material, missing a code requirement, ordering a fixture that does not fit), accessing trade pricing and vendor relationships that homeowners cannot get directly, and the design itself (a coordinated, considered finished space that reads as cohesive instead of assembled). Most luxury clients calculate the designer fee as a percentage of the project cost rather than an additional cost, because the design work saves more money than it costs in mistakes avoided and trade pricing accessed.