Pre NFL Draft Preparation

Listened to a radio interview recently and the head of a training facility was talking about all the NFL hopefuls that were there working on both on-the-field and off-the-field aspects. Among those there were several LSU players that are not expected to go high, if at all, in the draft. My question is, who is paying for these workouts? What if the player never draws an NFL paycheck? This facility brought in a lot of professionals and worked on things like wonderlic prep, nutrition and fitness, strength and agility, plus skills required to play your position at the next level. It was apparent the player was there for weeks. It's got to be a very expensive endeavor!