The cost of moving things is rarely the lifting
A filing cabinet dragged across vinyl leaves a mark that outlasts the clean. A desk shifted to reach the floor pulls a network cable out of a socket that nobody notices until the morning. A treatment chair moved a few centimetres no longer lines up with the power outlet it needs. None of these are heavy items in themselves; the problem is that the consequence lands on somebody else the next day.
There is also the question of what is inside. Cabinets holding records, retail display units carrying stock and shelving with equipment all become unstable when moved, and the person moving them cannot see the load. Working around is not a lesser service, it is the arrangement that avoids converting a cleaning visit into a damage conversation. It just needs to be stated so the result is not a surprise.
