What does an hour of your time actually cost?
Start with the hours, because this is where most pricing goes wrong. A working year is around 260 weekdays. Take off holiday, bank holidays, a fortnight of illness and slow weeks and you have perhaps 230 working days. Then take off the days spent quoting, chasing, buying materials and doing paperwork — for most trades that is a day a week, which leaves roughly 180 genuinely billable days.
Now the overheads: van, fuel, insurance, tools, phone, accountant, software, the pitches you did not win, training and certifications. Total them for the year.
Overheads divided by billable hours is what an hour costs you before you have earned anything at all. For most one-person trades that number is considerably higher than the figure they have been quoting from, which is why a busy year can end with nothing in the bank.