The pattern
The author names a cost or a benefit, then concludes whether something is good, bad, worth it, or will pay off, without weighing the other side of the ledger.
Partial premises. A whole-picture conclusion.
Two forms
Names a downside, then concludes the whole thing is bad or not worth it.
Names an upside, then concludes the whole thing is good or will pay off.
Two examples
Running
The gapOne cost named. No benefit weighed: cardio, longevity, mood, weight management.
Machine X
The gapTwo benefits noted. The operating cost, how much electricity Machine X actually uses, was never weighed.
How to spot it
The premise names a single cost or benefit. The conclusion jumps to a bigger judgment: good, bad, worth it, will pay off, the right call.
Premise covers a slice. Conclusion covers the whole.
At the answer stage
You cannot pre-list every cost and benefit the argument missed, so do not try. Stay flexible, and ask one question of the answer in front of you:
Should the argument have considered this cost or benefit before drawing its conclusion?
If yes, that is your answer.
Partial cost-benefit premises, a whole-picture conclusion.
Stay flexible. Ask whether the missing cost or benefit should have been weighed.