She says musicians are "having" to pay to play. They don't have to. They're choosing to, presumably in order to promote themselves. If they don't like the deal that's being offered, they don't have to do it. There are alternatives, such as promoting your own gigs.

The promoter is taking the bigger share, but he's also taking the bigger risk. As Bert points out, the promoter has overheads to cover whether or not the band brings in an audience. If the band flops, they don't really stand to lose much financially. It's also likely that an unknown band will have a fairly small core of fans, and the band is likely to do a better job of selling tickets to these people than the venue could. Setting a minimum quota ensures the band will make an effort to sell tickets.

The folk world doesn't (so far as I know) go in for "pay to play" but the notion of the unpaid floor spot is so well established that no one even thinks of it as exploitation. I'd go so far as to say that the opportunity to perform is part of what folk clubs are for. Nevertheless, the advice to aspiring performers is to do a lot of unpaid floor spots in the hope that they will lead to paid gigs. Is that so very different?