"Luxury" (noun) has a few meanings. 

 - The pleasure and comfort you get from expensive and beautiful things. 

 - Something expensive which is pleasant to have but not really necessary.

It is often paired with other words to create compound nouns.

 - Luxury apartment/car/yacht

 - Luxury cruise/hotel/resort

 - Luxury brands/goods/items/market

Luxury does not mean high quality but it is often considered to be. Luxury brands tend to be expensive because of their name, reputation and long history that has helped them to achieve a luxury status.

Labelling things "luxury" also adds a level of prestige that is not quite the same with labelling something "high-end" or "premium."

• "It's my dream to live a life of luxury. Not having to work or worry about bills."

"Luxurious" (adjective) - very comfortable and expensive.

• "We spent a few nights at a luxurious hotel in Singapore."

"Upscale" (adjective) - characteristic of or intended for the wealthy and are of good quality.

It can be used to describe anything but it is often used to describe buildings or areas.

• "Eve doesn't dress like she's rich but she lives in a pretty upscale neighbourhood."

"Opulent" (adjective) - expensive and luxurious, but it is often used to mean ostentatiously rich in appearance or showing great wealth. 

"Opulence" (noun)

"Opulent" is sometimes used in a fairly neutral way, but it is often considered negative and disapproving.

"Ostentatious" (adjective) - to show off your money, possession or power in an obvious way to attract admiration or notice. This is disapproving.

• "Castles look so gloomy and dark outside until you step inside and see how opulent all the rooms and furnishings are."

"Lavish" (adjective) - large in quantity and expensive or impressive.

"Sumptuous" (adjective) - impressive in a way that looks expensive.

To me, these are not as disapproving as "opulent."

• "The lavish wedding was followed by a sumptuous feast prepared by one of the best chefs in the country."

"Have money to burn" (idiom) - to spend a lot of money on things that are not necessary.

• "I don't know what they do but they certainly have money to burn."

"Have money to play with" (expression) - to have money available to use.

• "Since he paid off his car, he has more money to play with."

"The high life" (noun) - the exciting way of living where rich and successful people enjoy themselves by spending a lot of time and money in fashionable places.

• "Influencers look like they're living the high life on Instagram."

"Live like a king/lord" (idiom)

"Live high on/off the hog" (idiom)

"In the lap of luxury" (idiom)

All of these mean to have a luxurious way of life or to live in great comfort with plenty of money.

• "You can live like a king if you move to a cheap country."

• "It's a stereotype for people to live high on the hog when they become senior executives of a large company."

• "The royal family live in a lap of luxury in the palace."

"More money than sense" (idiom) - usually used in a humorous way describe people who wastes money.

• "Products and services that are labelled "luxury" often seem to be aimed at people with more money than sense."

"The jet set" (noun) - rich, fashionable people who travel around the world enjoying themselves.

A "jet-setter" (noun) is a member of the jet set. 

"Jet-setting" (informal adjective)

• "He was a jet-setting bachelor until he decided to settle down to start a family."

"Privilege" (noun) - the advantage that a person or group has, because they are rich or because of their position.

• "The country's elites are often more concerned with status and privilege than with the problems of the people."

"Socialite" (noun) - someone of high social class, who goes to a lot of parties and social events - usually they are wealthy and associate with other wealthy people.

• "It's common for socialites to interact with celebrities, politicians and industry leaders."