You might want to consider the cost of not upgrading legacy tech, UK's Department for Work and Pensions told

Processes relying on 1980s ICL mainframe contributed to 1bn pension black hole

Brit MPs have told the Department for Work and Pensions (DWP) it should factor in the cost of not upgrading a 34-year-old legacy system when reviewing tech investments after it contributed to a 1bn pension shortfall....