Lesson 4 of 8 · 8 min read · last verified 2026-08-26
Time is the other budget
In this lesson you will:
- Account for time spent alongside money paid
- Recognise tasks where the total cost exceeds doing it yourself
A subscription has a number on it, so it feels like the cost. For most people it is the smaller half.
The four costs of getting something done
Count all of them, or the arithmetic is wrong.
Money. The subscription or the metered charge. Visible.
Prompting time. Writing the request, and rewriting it when the first attempt missed.
Verification time. Reading the output properly and checking anything that matters. E4·L1 named this and this is where it gets a number.
Correction time. Fixing what came back, or doing it yourself after the third attempt.
A task that costs a fraction of a penny and forty minutes of your attention is not cheap. That is the calculation people skip because only one of the four terms arrives as an invoice.
Measure it once
Not forever — for a fortnight, on your three most frequent AI tasks. Two columns: minutes with, minutes without.
You will find, reliably, that some tasks are enormous wins and one or two are losses you had assumed were wins because they felt efficient. The feeling comes from the output appearing instantly. The forty minutes afterwards do not feel like part of it, and they are.
This is P1·L7’s evaluation discipline pointed at your own time.
Where time costs exceed the saving
Patterns worth recognising early:
Tasks you cannot check quickly. E4·L1’s rule. If verifying takes as long as doing, you have moved work rather than removed it.
Tasks where you know exactly what you want. Specifying it precisely enough often takes longer than typing it.
Short, familiar tasks. A two-line email you have written a hundred times. Opening a tool costs more than the task.
Anything needing three attempts routinely. Either fix the prompt properly (P1·L1’s examples usually solve it) or stop using it for that.
The subscriptions nobody cancels
A specific and very common waste.
People accumulate several paid AI subscriptions — one they use daily, one from a trial, one for a project that finished in March. Each is a small monthly amount and none is individually alarming.
Once a quarter, list every AI subscription you pay for and what you used it for last month. Cancel anything with an empty answer. You can resubscribe; the month you were not using it is not refundable.
Also check what your employer already provides. A surprising number of people pay personally for something their organisation has a licence for, because nobody announced it.
Free is not free of time
The counterpart, so this is even-handed.
Free tiers cost you queue time, lower limits, slower models and the effort of working around caps. If a paid tier removes an hour a week of friction, the comparison is not “free versus £20” — it is “£20 versus an hour a week”.
For some people that is obviously worth it. For others the free tier genuinely covers the work. The point is to compare the same quantities on both sides, which is what almost nobody does.
Try it now (5 minutes)
List your AI subscriptions and what you used each for in the last month.
Then take your most frequent AI task and estimate, honestly, the minutes it takes including checking. Compare that to doing it yourself. One of your tasks will surprise you.
Check your understanding
Recap
Count all four costs — money, prompting, verification and correction — because only the first one is invoiced. Measure your three most frequent tasks for a fortnight and expect one supposed win to be a loss. Audit subscriptions quarterly and check what your employer already provides. And when comparing free against paid, put time on both sides of the equation.
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