What makes an expensive speaker expensive

The difference between a very good expensive speaker versus a very good inexpensive speaker is usually size and ability to go full range in larger rooms.

There is a lot that can go into making a good speaker. Both the sound and the aesthetics. Also the reliability. In the end willingness of customers to pay for whatever reason is mostly what determines how expensive a product is, including speakers. Values differ by person so anything is possible. The goal of marketing is to help make people more willing to pay for advertised benefits by appealing to the values of the target market segment. The more one is willing to pay the more profit per unit. Thus high end audio was conceived, a boutique industry where units are fewer and  prices generally higher.

Most people, myself included, don’t have rooms big enough to justify the most expensive home speakers which mostly tend to also be the largest.

If I did have an exceptionally large room that I could not cover for reasonable cost with home audio products I would look towards pro audio gear designed for larger venues for best chance at top notch sound for reasonable cost.

Of course if cost is no object then the world is your oyster....