Week 10 — Should You Wait?

Waiting for a better price is a bet, not a guarantee. This week introduces expected value: a simple way to combine the chance of a discount with the size of that discount.

28 September 2026

Core question#

When does it make sense to wait for a better price?

Week 5 showed price moving over time; Week 6 showed it responding to context. Put together, next month’s price cannot be known for sure, but you can still make a reasonable estimate. Waiting is a bet on possible future prices, and you can judge that bet even when the outcome is uncertain.

Expected value#

The expected benefit of waiting is not “the discount, if it happens” — it’s the discount adjusted by how likely it is to happen:

expected saving = probability(better deal) × size of that deal

A 10% chance of a 40% discount has a smaller expected saving than a 50% chance of a 15% discount, even though the first sounds more dramatic. This is the same reference-price discipline as Week 3: the size of a hoped-for discount means little unless you also ask how likely it is.

What waiting costs#

Waiting is not free just because no money changes hands during it:

• Stock-out risk — the item, or this specific model, may not be available at any price by the time you’d act.
• Urgency — if it’s needed by a fixed date, the window to wait may be shorter than the window a “maybe” discount needs to appear in.
• The value of having it now — a want satisfied today is not interchangeable with the same want satisfied in six weeks, independent of price.

None of these can be predicted perfectly. The goal is not to forecast the future exactly; it is to make these costs visible instead of ignoring them.

The $249 headphones#

Hypothetically: a shopper hears that this model “usually” goes on sale around a known annual event, six weeks away. That’s a genuine input — a probability and a rough discount size can be estimated from it — but it is not a promise, and this course makes no claim about any real product’s actual future price. Week 11 turns this exact situation into a calculator: given a price, a rough probability, a rough discount size, and how much the wait itself would cost, should this shopper wait or buy today?

The rumoured sale is invented for this example. This course makes no claim about any real product's future price, and a shopper's "usually" is an impression, not a dataset.

Learning outcomes#

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

• define expected value in terms of the probability and size of a future discount
• compute expected saving from waiting given a stated probability and discount size
• name stock-out risk and urgency as real costs of waiting, distinct from the money saved
• explain why future prices can be estimated but not known in advance
• decide, given a stated set of assumptions, whether the expected saving clears a stated bar for waiting

Before class#

Think of one purchase you’re currently, or recently were, putting off in the hope of a better price, and write down your honest best guesses for: how likely a discount is in the timeframe you’d wait, and roughly how large it would be.

In class#

Using the numbers you brought, compute expected saving as probability times discount size, then decide as a group whether that number is big enough to justify waiting — and state explicitly what would have to change, in probability, size, or urgency, to flip your answer.

What you should leave knowing#

Waiting is a bet you can calculate roughly. A small, likely discount can be better than a large, unlikely one, and neither is guaranteed.

This week has a full lecture — Lecture 4: Should You Wait?, whose slide deck walks through the expected-value calculation above in detail, and whose reasoning feeds directly into Assessment 3, Build a Buying Engine.

Where this goes#

Week 11 adds the missing piece: waiting isn’t free even when the wallet doesn’t notice, because time itself has a price.