The point "Estimated costs" in the O&M recommendations is meant as a guideline for the O&M organisation that are going to take care of the building afterwards.
The entered price can be used to take active choices in the planning of the maintenance, quickly after the handover of the building.
An important element for some builders is to have a fair guess at what a maintenance activity should cost, and therefore they would like to have an estimated price for the O&M activity.
It's not possible to estimate the price of all types of Objects. If this is the case, you'll often dialogue with the builder or the administrator.