Procurement costs
Warranty hassles
Lost productivity (problem caused)
Insurance
Phone system usage
Shipping & Receiving
Accounting costs
Cost of money
Occupancy
Electricity
and a whole lot more.

Most people who say Gartner's figures are way too high have no idea how to identify and allocate costs. Companies that do have that ability generally confirm Gartner's figures.

Computers can be effective tools, but they are very expensive tools.