Economics · Lesson e01

What Is Something Really Worth?

You can't buy everything — so every choice quietly costs you something else. That hidden cost is where economics begins.

A girl at a market thoughtfully choosing between a grooming brush, a sketchbook and a cinema ticket

Welcome to economics. It sounds like it's about money, but really it's about a problem everyone has: there is never enough time, money, or stuff to have everything you want. So people are forced to choose — and economics is the study of how they choose, and why. Once you learn to spot the hidden cost behind every choice, you'll never look at a price tag the same way again.

💡 Big idea 1 — Scarcity

Scarcity means wants are unlimited but resources are limited. Mia would love a new saddle, riding lessons, a sketchbook, and a trip to a horse show — but her pocket money only stretches so far. That gap between "everything I want" and "what I can actually get" is scarcity, and it's the reason economics exists.

Needs vs wants. A need is something you must have to live (food, water, shelter, warmth). A want is something that makes life nicer but you could survive without (a new bridle, a phone upgrade, sweets). Telling them apart is the first move in any smart money decision — needs come first.

💡 Big idea 2 — Opportunity cost

Because you can't have everything, choosing one thing means giving up another. The opportunity cost of a choice is the value of the next-best thing you gave up.

If Mia spends her €18 on a grooming brush, and the next thing she'd have bought was a €15 sketchbook, then the real cost of the brush isn't just €18 — it's also "the sketchbook I didn't get." Every yes is also a no.

Maths connection: economics runs on the maths you already have. A budget is just subtraction (money in − money out). Comparing prices in different countries is ratios and exchange rates — the same proportional reasoning from Lesson 13. And "is this worth it?" is really the number-sense question you always ask: is this reasonable?

Worked Examples

Worked Example 1 — finding the opportunity cost

Mia has €30. She's deciding between three things she wants: a grooming brush (€18), a paperback (€15), and a cinema ticket (€12). She buys the brush. What is the opportunity cost?

Step 1 — what did she give up? With €30 she couldn't buy all three. After the €18 brush she has €12 left — enough for the cinema, but not the €15 book.

Step 2 — name the next-best thing given up. The most valuable thing she passed up to buy the brush was the book (€15). So the opportunity cost of the brush is the book she didn't buy — not the €18 price, but the next-best option lost.

Worked Example 2 — comparing prices across currencies

The same saddle pad is sold for $25 in the USA, €22 in Spain, and £20 in the UK. Roughly, $1 ≈ €0.90 and £1 ≈ €1.15. Where is it cheapest, in euros?

Convert everything to one currency (euros) so you're comparing fairly:

$$\$25 \times 0.90 = €22.50 \qquad £20 \times 1.15 = €23.00$$

So in euros: USA €22.50, Spain €22.00, UK €23.00. Spain is cheapest. Notice you couldn't tell just from the numbers 25, 22, 20 — you had to convert first. That's proportional reasoning doing real work.

Warm-Up

Problem 1

Sort these into needs and wants: (a) clean drinking water, (b) a new horse-riding helmet upgrade when the old one still fits, (c) winter boots when hers have holes, (d) a second sketchbook, (e) food, (f) cinema tickets.

need or want for each →
Problem 2

In one sentence each, explain: (a) what scarcity means, and (b) why scarcity forces people to make choices.

define in your own words →
Problem 3

Mia has 2 free hours on a Saturday. She could ride her horse, finish a drawing, or watch a film — but only time for one. She chooses to ride. What is the opportunity cost of riding? (Hint: opportunity cost isn't money here — it's time.)

what did she give up? →

Core Problems

Problem 4

Mia has £24 of pocket money. She wants: riding gloves (£16), a comic (£7), and a smoothie (£4). (a) Can she buy all three? (b) If she buys the gloves, how much is left and what can she still afford? (c) What is the opportunity cost of buying the gloves?

add up totals → subtract → name what's given up →
Problem 5

A grooming kit costs $36 in the USA and €30 in Germany. Using $1 ≈ €0.90, convert the US price to euros and say which country is cheaper.

convert $36 to € → compare →
Problem 6

At a horse show, only 40 rosettes are printed but 200 riders want one — so the organiser sells the last few at auction and they go for a high price. Use the idea of scarcity to explain why the rosettes became expensive. What would happen to the price if they printed 500 instead?

link scarcity → price → then more supply → price? →
Problem 7 Challenge

Mia earns €6 per week walking a neighbour's dog. She's saving for riding boots that cost €54. (a) Write an equation for her savings $s$ after $w$ weeks. (b) How many weeks until she can afford the boots? (c) A friend offers her €6 per week for the same time slot to help at an art studio instead — which she'd enjoy more. If she takes the dog-walking money, what is the opportunity cost?

write $s = 6w$ → solve for the boots → name the opportunity cost →
Problem 8 Open

You have a €100 budget to get everything ready for a weekend horse show (entry fee, travel snacks, a small gift for the stable owner, a treat for yourself). Make a spending plan that stays within €100, list what you chose not to buy, and name the opportunity cost of one of your choices. There's no single right answer — explain your thinking.

your budget plan →

Think like an economist 🧠 — There's no such thing as "free." Even a free gift costs you the time to collect it, or the space to store it. Whenever someone says something is free, an economist quietly asks: "free — but what did it really cost, and who paid?"

Show answers

Problem 1

Needs: (a) water, (c) winter boots with holes to replace, (e) food. Wants: (b) helmet upgrade (old one still fits), (d) second sketchbook, (f) cinema tickets.

Problem 2

(a) Scarcity = wants are unlimited but money/time/resources are limited. (b) Because you can't have everything at once, you must choose which wants to satisfy and which to give up.

Problem 3

The opportunity cost is the next-best thing she gave up — either finishing the drawing or watching the film (whichever she'd have picked next). The cost of riding is measured in the best alternative use of that time.

Problem 4

(a) No — £16 + £7 + £4 = £27 > £24. (b) After gloves: £24 − £16 = £8 left — enough for the comic (£7) or the smoothie (£4), but not both. (c) Opportunity cost = the next-best thing given up, e.g. the comic + smoothie she can no longer both have.

Problem 5

$36 × 0.90 = €32.40. Germany (€30) is cheaper than the US ($36 ≈ €32.40).

Problem 6

The rosettes are scarce (40 for 200 riders), so people compete and bid the price up — high demand + low supply = high price. If 500 were printed, they'd no longer be scarce (more than enough for everyone), so the price would fall, probably to almost nothing.

Problem 7

(a) $s = 6w$. (b) $54 = 6w → w = 9$ weeks. (c) Opportunity cost = the art-studio work she'd have enjoyed more (and any non-money value that came with it) — the money is the same, so the cost is the more enjoyable alternative given up.

Problem 8

Open — any plan totalling ≤ €100 is valid. Look for: a clear list with prices adding to ≤ €100, at least one thing deliberately left out, and a correctly named opportunity cost (the best item she chose not to buy).

Next up → e02: Supply, Demand & Why Prices Move You saw in Problem 6 that scarcity pushes prices up. Next we'll turn that into the single most famous idea in economics — supply and demand — and use it to explain why concert tickets, strawberries in winter, and a rare horse breed all cost what they do.

What Is Something Really Worth?

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