I had a co-worker years ago that got a sponsorship from a well known clothing brand. Ended up quitting his job where we worked, but had a "session" on his last day in our warehouse that just blew us all away. This guy was talented, but never made it to the superstar elite status. From what I heard the sponsorship was about double of what we made when he was holding the job with me. There was insurance policies that came with doing the stunts which probably would cost a lot but I'm not sure if it was covered by the sponsor.
The funny thing was that in his last two weeks with the company, he plastered stickers of his sponsor's all over the place. On forklifts, racking, inside binders and paperwork - and the best one - about 40' on the underside of a covered roof area outside that could not be reached in any way besides an elaborate scaffolding. Still wondering on how he did that one.....

If you think it's neat seeing it on Youtube, you should see it in real life without editing. There are usually never any spills unless there is major competition and prize money and the riders are performing riskier tricks.