One of the many variations in definition of luxury is an item that is considered to be an indulgence, as opposed to a necessity.
Aside from basic clothing, food, and shelter, everything we use on a daily basis is ultimately a luxury.
Indoor plumbing, hot showers – these are luxuries.
When someone thinks of a luxury, more often than not, these everyday items are not seen as luxurious – instead, opulence, grandeur, riches – these are what are imagined. Gatsby. Scarlet after she marries Rhett. These are the images that come to mind.