If they're finished, running models then they are RTR. Even Bachmann and Hornby products are, ultimately, a kit of parts assembled by the manufacturer. The price of the Silver Fox products merely reflects the fact that they are not manufactured in volume using cheap far eastern labour.
Well that logic makes even you a kit of parts, on the chromosome level...
One is mass produced, and benefits from the cost savings mass production give, the other is a kit that will have been individually hand built, which is more labour intensive and thus costs more - as the price-point amply shows!