RAAM is a VERY expensive undertaking. Having the younger sister of the Duchess of Cambridge (who will likely one day become the Queen of England) is a great strategic move by the team, as it will raise the team profile for potential sponsors as well as for potential donors to their charity. Plus she's wealthy enough to chip in for the massive costs.
Also, an aside: interesting this year to see how well the British have been doing, with a rider in 2nd place men's solo (Mark Pattinson) and in 3rd place women (Shusanah Pillinger) and 3rd place 2-man team. In addition to that 8-person Royal team!
Luis