Do the math...
"At 30 June 2012, NBN Co’s headcount was 1,674" according to NBN Co Annual Report 2012.
The number may have gone up or down, but let's work with that number.
100'000 AUD / 1674 = 59.7... so let's say 60 AUD per head.
What's 60 AUD in time? Counting conservatively, I guess an hour.
I think it is safe to say that having the coffee machines saves more than an hour of work time per employee/consultant a year, not to mention side benefits of people talking work problems around the coffe machine.
And of course my calculation is ridiculously conservative as the 100'000 AUD include the purchase of the machines, a cost which should probably be split over several years.