Well it's fairly simple - we have a building that only has office people in (not many, but some)

The cost of that building divided by the number of people there.

There's then power, heat, cleaning, etc, but that's all small fry compared with the rent or opportunity cost of an office building.

The technical infrastructure (Cisco switches don't come cheap) is probably offset by the cost of supporting remote infrastructure, vpns etc.

The cost per deal in central London is on the order of $10k-$20k a year. I'll take that in cash thanks.

http://www.cityam.com/233082/london-office-rents-tube-map-he...