are willing to pay for the opportunity to be part of the BYU football program and for the change to actually play...and for the quality (and inexpensive) BYU education and lifestyle.
BYU has a long history of walkons earning playing time and even landing a starting role.
There are also a lot of BYU walkons who never pan out. I'm sure some of them regret the decision...but many enjoy being part of the BYU football program and their BYU experience, even if they don't ever contribute to the team and may be would have made a contribution at some other school had they chosen to go there. There are myriad examples of this scenario at BYU over the last 20 or 30 years.