For the type of person that buys this stuff, it is the price that makes it better.
It satisfies the need to feel successful or projection of high status for the person that has underly low self-esteem or inferiority, or some psydo-internet-pop science that I happily admit I do not understand.
I don't know what the motivation is in this case. If I had silly amounts of money I would probably spend a silly amount of it on equipment.
Waters are muddied here as she is a dealer, and although it is made clear these are her personal systems she will have paid trade price, and so could sell it on for no loss or even still a small profit; she may even have bought it through the business so the resale value is on the books as an asset..
Plus we don't know that she also uses the systems to demo to clients so serves a practical purpose with regards to her business and is not just for personal use.
That would also explain the use of pointlessly expensive cables and racks, the accessories are the sweetest plum in terms of profit margins. We don't know if she really thinks they do anything, If she is selling them she is never going to say they are of no value to the sound and will of course want to show clients that she uses them herself.
You can't blame the salesman (or saleswoman) for selling, they are just doing their job. It's the customer's responsibility to do due diligence before entering the salesroom.
The presenter of the video, on the other hand, seems to take for granted that high price = good sound and the more spent the better the sound gets. The tone of his comments indicates that he assumes his viewers feel the same way i.e there is a lot of 'Look at this lads, don't you wish you could afford it?'