Bandwidth is not the main cost, it's running the CPUs at 100% for most of the day. A modern CPU at idle might consume 60 watts but at 100% take 160 watts. That 100w difference times 5000 machines makes for a big jump in the electricity bill. At 10c per kW/hr, that's $50/hr. If they were running 20 hrs a day, he was costing the district $1000/day.
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