Expensive Luxury Gadget

In economics, a luxury good is a good for which demand increases more than proportionally as income rises, and is a contrast to a "necessity good", for which demand is not related to income.
Luxury goods are said to have high income elasticity demand: as people become wealthier, they will buy more and more the luxury good. This also means, however, that should there be a decline in income its demand will drop. Income elasticity demand is not constant with respect to income, and may change sign at different levels income. That is to say, a luxury good may become a normal good or even an inferior good at different income levels, e.g. a wealthy person stops buying increasing numbers luxury cars for his automobile collection to start collecting airplanes (at such an income level, the luxury car would become an inferior good).