Six admin hours a week, over a forty-eight-week year, is 288 hours. At £250 an hour that is £72,000 of expertise applied to work that does not need it.
That figure is arithmetic on an assumed rate and an assumed number of weeks, not a measured result. It is worth running with your own rate, because the number sets a realistic ceiling on what fixing the problem is worth spending.
This works best if you bill at £150 an hour or more, have three or more live client relationships at once, and have tried tools without connecting them into anything that runs. It is a poor fit if you are newly independent and still finding your first clients, or if your work is so bespoke that no two engagements share a process.