In your post history it looks like you have never mentioned his name so I can't actually prove you know that name or have any idea who the player is. Would it be reasonable for me to assume you have no idea who Curtis Brown is? Of course not. The reasonable assumption is that you know exactly who he is based on the fact you are on this board talking about BYU football with years of fandom.
This is no different. I can't see the exact contract details but I do know how much Nike is paying other institutions across the spectrum of college football. Since I can't prove Nikes contract with BYU is at all similar to these institutions I can't prove they paid for the uniforms but assuming that they are not is not a reasonable assumption. The reasonable assumption is that like everyone else, BYU has a pretty templated contract with Nike that funds these one off uniforms.
Enjoy.