At the end of the day it comes down to convincing the customer and most times the customer is convinced. Whether they keep there new expensive vacuum is a different story.
I can only speak for my country , I just looked through our a few of our local on-line classifieds, 35 Kirby sentria's for sale 12 other older kirby models, 14 of the sentrias claim to be hardly used bought with in the past 6 months with slips to prove it.( I checked not the same customers ) This tells me one thing , That customers are easily wowed by the sales ticks but like many of my customers who have traded in one find it to cumber sum to use day to day. I have a commercial twin motor tank vacuum with a PN on it, It will not only out clean the kirby but suck it up too, I tried to make a separator tank for it using a 55g oil drum and it crushed it with its suction. Best yet I could by 4 of them for the price of One Kirby but its impossible to use and inconvenient.
At the end of the day it doesn't matter how well it cleans when it is to much effort to use it, remember some people just don't enjoy vacuuming ( shocker )
One thing is did see aswell, you will battle to find any one selling there Rainbow, Miele, Dyson, Sebo or thermax. There was one of each for sale, all old models