Alex Tabarrok asks and answers.
One thing I think he doesn't emphasize enough: the entertainment unions have been clever enough to give their members no incentive to defect. Unlike in many unions, top members are not slaves to seniority or scale. The unions set a floor on talent pay that is low enough that it does not come out of the pay of the stars. The ultimate cost of the high union scale is probably paid by consumers of extremely low budget indie films that now have to be made without union talent; this makes the cost of unionization the next best thing to invisible, and college students with excessive tattooing are at any rate not a very powerful constituency against a union.
I like your reasoning Megan but it begs the question- if that lack of "slave to seniority or scale" works for the WGA and other Hollywood unions, why has it not been adopted by other unions in other industries?
Might I point out, these are the Writers GUILD of America, the Screen Actors GUILD, & the Directors GUILD of America. As opposed to the Teamsters UNION, etc.
Most unions evolve a philosophy that assumes that all workers with the same certification or in the same job are equal. E.g., teacher's unions valiantly resist merit pay, any means of rating different teacher's performance (output) instead of credentials (input) because it might lead to merit pay, and often even endeavor to prevent the firing of teachers that are flat-out incompetent in spite of their certifications. Such leveling of pay regardless of performance leads to superior performers being underpaid to subsidize the below-average - and to superior performers looking for other jobs. The public schools can survive that only because they get their tax money whether or not they serve their "customers" well.
In a competitive business environment, a manager that allowed this situation to persist would first lose his good workers, then many of the average workers, and then his customers and his job. So both the superior workers and the business owners and managers will fight the unions on this issue - even if it means closing one business and opening another one elsewhere.
Hollywood unions can't fall into this trap because it's too obvious that all actors, writers, etc., are not equal. Even doctrinaire socialist union leaders realize that stars aren't going to work for union scale, and if you press them too hard they would not only leave the union shops, but the financiers and the fans would follow them. OTOH, it doesn't cost the stars anything noticeable to sign a union contract that gives the lowest tier of studio workers a good hourly pay rate and a tiny share of the residuals. Maybe Brad Pitt will get only $60 million when he could have got $60.1 million if the extras were working for minimum wage, but he's rich enough anyway and supporting this system helps him feel better about himself. Generous pay also helps the studios be sure that, even though a character actor has been working as a waiter for six weeks since his last one-day acting job, he'll happily skip out on the restaurant when the studio calls...
So Hollywood unions have power because circumstances have made them wise enough not to misuse it, and thus no one with the power to fight them has a reason to.
Lady, you really don't have any fucking idea what you're talking about, do you?
Why the fuck is the Atlantic paying for this gibberish?
There's a nice example of unions making life difficult for 'indie' filmmakers in Lost in La Mancha (not that it makes much difference when God's got it in for you anyway).