Height changes what the task involves
High-level dusting in a converted warehouse is not the same activity as dusting a ledge. It involves working at height, which brings equipment, training and planning requirements that do not apply to the rest of the arrangement. A provider quoting it as a line item without mentioning any of that has either not considered it or intends to arrange it through somebody else and neither answer is unacceptable provided it is stated plainly.
Ask what equipment they propose: a scissor lift, a scaffold, an extension system used from the ground, or something else. Each has implications for floor loading, access to the area, the time required and whether the space can be used while the work happens. Those answers tell you whether the provider has planned the task or simply included it and whether the frequency they propose is actually achievable.
