Greenlight I think do the donkeywork and Duke do the selling.
I remember when this years TT dvd went on sale from Duke @ 19.99 ish on another motorcycling website somebody said to order from play.com I think price was 11.99 so there is £8 saving straight away and freepost and packing and arrives in a couple of days. In this day and age when you can buy blank cd's/dvd's cheaply, for the companies it must only cost pence to burn a disc so there must be a very large profit to be made.
Maybe be an opening for someone starting off I am sure S100 and MGP would be interested.