Every product has a hidden sensitivity setting. Raise the price a little — does demand collapse, or does it barely budge? That sensitivity is what economists call elasticity. And once you see it, you'll understand why companies price things the way they do, why some industries are brutal to compete in, and why governments taxing cigarettes doesn't actually stop many people from smoking.

That's exactly why the gas spike and the streaming hike landed so differently — and it comes down to three things. First: substitutes. If there are easy alternatives, demand is elastic — you'll switch. No alternatives? Inelastic. Second: necessity versus luxury. Insulin is inelastic. A spa day is elastic. Third: time. In the short run, demand for almost everything is inelastic — people haven't adjusted yet. Give it a year, and people find workarounds. Gas demand appeared inelastic after the 2022 price spike, but over two years, EV sales jumped and people moved closer to work. Time turns inelastic demand into elastic demand.

Supply has elasticity too, and it's just as important. If prices rise, can producers quickly make more? If yes — elastic supply. If factories take years to build and raw materials are scarce — inelastic supply. This is why housing prices in cities like San Francisco or London stay brutal even when demand drops slightly. Supply is almost completely inelastic: you can't just build 50,000 apartments overnight. So price stays high. Meanwhile, t-shirt supply is highly elastic — factories can scale up fast — so a surge in demand gets absorbed quickly without prices exploding.

There's one more twist that changes how you see the world. When demand is inelastic, raising prices actually increases total revenue — you lose a few customers but make more per customer, and the math works out. When demand is elastic, raising prices kills your revenue — too many people leave. This is why luxury brands sometimes raise prices on purpose. It signals exclusivity, and their customers — who are buying status, not just a product — are deeply inelastic. And it's why budget airlines compete on price so aggressively: their customers are extremely elastic, and even a $10 difference sends them to a competitor.