Week 11 — Your Time Has a Price

Search, travel and waiting all take time. This week builds a calculator that weighs time spent against possible savings.

5 October 2026

Core question#

How much effort is worth spending to save money?

Week 10 priced the uncertainty of waiting. This week prices the time waiting takes. Search cost, travel cost, and time spent watching for a lower price are all real costs. They become easier to compare once you put a dollar value on an hour of your own time.

Opportunity cost of time#

If your time is worth $20/hour doing anything else you’d rather be doing, then two hours spent comparison-shopping to save $15 has already lost money before you’ve bought anything: $40 of time against $15 of saving. This isn’t a claim that comparison-shopping is pointless — it’s a claim that it has a point where it stops being worth it.

The sunk-cost trap#

Hours already spent searching feel like they should count toward the decision — “I’ve already spent three hours on this, I might as well keep going” — but they are a sunk cost: spent regardless of what you decide next. The only hours that matter for the next decision are the hours you have not spent yet.

A working example#

The tool below combines Week 10’s expected-value framing with this week’s time cost. It asks for hours already spent purely to make a point: watch what happens to the recommendation when you change that number versus when you change any of the others.

The $249 headphones#

The shopper from Week 10 has already spent three hours reading reviews and comparing listings. That’s sunk. What matters now is: given the estimated 30% chance of a 15% sale, 14 days of runway, and roughly two more hours of watching required to catch the sale if it happens — is it worth it? Change the value of an hour in the tool above and watch the recommendation flip.

The 30% probability and 15% discount size are invented for this example. They are the kind of estimate a shopper would have to supply themselves, not figures this course has measured.

Learning outcomes#

By the end of this week, you should be able to:

• compute the opportunity cost of time given a stated value per hour
• explain why hours already spent searching are a sunk cost excluded from the next decision
• use the buy-or-wait tool to see how the recommendation changes as one input changes at a time
• combine Week 10’s expected-value framing with a time cost to reach a single recommendation
• state the break-even point at which further searching stops being worth it

Before class#

Estimate, honestly, how many hours you’ve already spent — searching, comparing, waiting — on one purchase decision you’re currently facing or recently made, and separately, what you’d value your own hour at for the purposes of this exercise.

In class#

Enter your numbers into the buy-or-wait tool above, or a classmate’s if you don’t have a live decision right now, and change one input at a time — hours already spent, value per hour, probability, discount size — noting which single change flips the recommendation and which don’t move it at all.

What you should leave knowing#

Hours already spent are gone regardless of what you decide next, so they don’t belong in the forward calculation — only the hours you haven’t spent yet, and what they’re worth, do.

Where this goes#

Week 12 puts everything — price, quantity, discounts, history, context, subscriptions, points, alternatives, uncertainty, and time — into one final decision.