Another trick used by main dealers (one in particular) is to buy manufacturer's ex-personnel cars; cars which have been registered as being owned by the manufacturers. The main dealer then takes the vehicles into stock but issue some of the vehicles to the staff, sometimes for up to three or four years use. Having first taken it in as stock, the mileage is recorded as when they received the vehicle...not when the staff member has finished with it, so the initial advert always states the 'original' mileage so as to attract viewers. And of course, because they are a 'stock' vehicle they do not have to be registered in the dealers' name, so when it gets sold to Joe Public, it only has 'one owner' despite having been 1) A company car; and 2) A dealers hack and runabout in addition being a company car.
They charge new prices for second hand bikes. I bought a Speed Triple from Fowlers, put 3000 miles on it, traded it in for a Streetfighter at Riders (for a fair price I have to say) and the last time I looked they were punting it out at £300 more than I paid Fowlers for it. Nice work if you can get it.