Descaling a steam oven at from $145, servicing a heat-pump dryer’s condensate path at from $135, and the maintenance visit at from $145 that includes cleaning refrigeration condensers. Between them they are the cheapest items here.
What they prevent is the steam water-system repair, the heat-pump circuit and the refrigeration sealed system — the three most expensive rows on this site, one of which starts at $495. In this water and this humidity that is arithmetic rather than advice: the descaling interval this appliance calculates is based on softer water than the supply here, and a ventless dryer in a closed closet loads its condenser faster than any manual assumes.