I was going to start a thread on what's in cheap for us to classify blends as such. In other words, what makes cheap cheap, and vice versa (what makes a good quality fragrance such a blend).
It is related to your question, what makes luxurious luxurious.
2-. Technical aspects
We will perceive niche offerings as luxurious because of the price, packaging, stores where they are sold, comments from aficionados we consider savvy in perfumes, origin, nose in charge, the house behind the scent, etc.
To these, add some objective qualities: complexity, for example. You can actually tell if the scent is good quality if you can perceive how notes morph along time. Add to this the way notes blend, they don't feel discordant. Plus physical reactions: you won't get the feeling of needles in your nostrils, or headaches, or a scratchy feeling in them.
These objective qualities are related to perception. It is the "hen - egg" discussion.
I used to work in marketing research. We would conduct product tests for wine companies among established aficionados. Enologists laughed really hard at them, for aficionados radically change their minds on product quality as soon as brands were introduced: a branded wine would be ranted, but highly classified when tried blind.
Cheating people can be amazingly easy.
Going to the point: luxury is a social construct that is backed by hefty prices.