Not always. There are a number of reasons buyers or sellers use dealers. e.g. warranty, finance, partex, location, going to a commercial premises rather than a home, may deliver, consumer protection, reputaton for only selling good cars so no time wasted visiting loads of cars, safe money transfer etc etc
Many of us may not value these but some buyers do. So they may happily pay an extra £500 or £1000 for some or all of the above. It's not just he value of the car but the overall package. I know of plenty of people who will never buy or sell cars privately because they don't want the 'risk' or 'hassle'. Same as there are people who will only buy a car new or with manufacturers warranty.
It happens everyday with mainstream cars - why should it be different with Westfields? Caterham have two authorised dealers for their cars.
I bought my first Westfield 15 years ago from Terry Nightingale. He had the car I wanted at roughly the right price and in those days he had 10 different cars in stock that I could sit in and try out. He was on my doorstep and it saved me spending several weekends driving around the country.
David