(I might need to separate out Burden of Ownership and Maintenance Cost, as system maintenance cost seems to be a bit different than burden of ownership)
Aside from standard maintenance cost, owning or having possession has a derivative cost of maintenance and storage. This cost may be spatial, mental, financial, or what have you.
I suspect this cost is often underestimated. A notable exception is large purchases like cars and homes, where we do reasonably try to include the maintenance and ownership costs over time.