There is an article is a past ITG journal, I can't remember which one, but it talks about this subject. Basically, it says that the corporations who sponsor artists DO NOT give them free trumpets, money, etc. Maybe a discount, but not a whole lot. I think that the purpose for this relationship is mutual recognition. Here's an example: Jens Lindemann is a Yamaha Performing Artist. He plays Yamahas exclusively. He gives the company a great reputation with his awesome playing. In return, they advertise him on big banners, their website, etc. His name gets out there because he is sponsored by a large, highly-reputable trumpet manufacturer. It's a win-win situation, but I do not think that he receives much compensation, if any, for playing Yamahas. Of course, the only way to know is to ask him yourself.