If you really want to break it down, on a small movie everybody knows that they're there for artistic reasons to do something special to make something amazing, and they're not going to get their normal hotel and they're not going to get their trailer, but they're willing to forgo that - and of course the salary - because they want to do something really special. On a big movie, most people are getting paid a lot of money, and so they're there to do the work.