Opportunity Cost Thinking
Mental Model #7 · Charlie Munger
You chose
Vendor deal at 5% return
Return
5.0%
Visibility
Visible
Effort
High
▲ Selected path
Best alternative
Index fund at 10% return
Return
10.0%
Visibility
Hidden
Effort
Low
✦ True benchmark
Real opportunity cost
−5.0%
The gap between what you chose (5%) and your best forgone alternative (10%) is the true price of the decision — invisible on any invoice, but real on every balance sheet.
⚖️
Always compare
No decision exists in isolation. Every option has a shadow — the best alternative you didn't take.
🎯
Set a hurdle rate
Munger & Buffett use Treasuries + spread as a baseline. Anything below it doesn't deserve capital.
🕰️
Time is currency
Every hour spent on mediocre work, meetings, or people has a cost: the better use you skipped.
"All intelligent investing is the comparison of one investment with another — and the alternative is always sitting right there."
— Charlie Munger, Poor Charlie's Almanack