The problem with this as a framing device is that it doesn't describe very many working musical acts. 360 deals are probably generally gross? But Pemberton's situation is weird. In most cases, labels are in fact going to lose money from midlist acts.
The more you look at these kinds of businesses the more striking the pattern is. It's true of most media, it's true of startups, it's true for pharmaceuticals. The winners pay for the losers; in fact, the winners are usually the only thing that matter, the high-order bit of returns.
What's challenging about this is that you can't squeeze blood from a stone. The package offered to a midlist act might in fact be a loss leader; incentive to improve dealflow and optionality for the label, to get a better shot at the tiny number of acts whose returns will keep the label afloat. There may not be much more to offer to acts that aren't going to generate revenue.
David Lowery (a mathematician and the founder/lead vocalist of Camper Van Beethoven and Cracker) had an article about this years ago:
https://news.ycombinator.com/item?id=3850935
It's worth a read (though things have probably changed in a number of ways since then). It's an interesting counterpoint to the automatic cite to Albini's piece that comes up in these discussions. Not that you should have sympathy for labels, just it's useful to have a clearer idea of what the deal was. The classic label deal with a mid-sized advance that never recouped (and which the labels never came back looking for when it didn't) was basically the driver for "middle-class" rock lifestyles; it's dead now.