All wares whose demand increases disproportionally with an increasing income.

Bread for example is not a luxury. If you were to earn twice as much, you wouldn’t buy much more bread than you already do. The same isn’t true for jewelry for example.

something that is objectively unnecessary but gives comfort or at least the illusion of comfort

i think of it like the laws of diminishing returns

think of a shitbox $3,000 used car. assuming the engine is more or less running, you get like 80% of the benefits of a car

it gets you from point A -> B - the primary purpose of a car

then you spend another $10,000 for a $13,000 5~6 year old Toyota or something. now you have A/C, that gives you an extra few % benefits. You get a carplay so you have a nice little screen for a GPS, another few %. you get a key that unlocks your car, etc.

so you went from 80% to lets say 90%. but that base 80%, getting you from point A -> B hasn’t changed.

that extra $10,000 bought you 10% extra

then let’s say you spend another $100,000 for a $113,000 car

you get all the benefits of the previous cars, but you maybe can speed up a little faster. you have heated seats. you have a sport mode or something.

that extra $100,000 bought you another like 7% so now you’re at 97%

Luxury is that last 20%. The closer you wanna get to 100%, the more expensive each % costs. This is a status symbol