The mount.
Seriously, is there people really doing this roulette for the mount?
I am a casual player, and I do the mentor roulette maybe once or twice a week when I think about it and when I have time. Just to help people.
Assuming someone with more playing time and doing the roulette twice a day, this person will need 3 years in order to get the mount.
Assuming now a crazy guy doing 20 roulettes a day (so something like 10 hours a day doing only this), he will need 3 months. Is there people crazy enough to do that only for a mount?
...
I think no one is doing this roulette for the reward.