> We're trying to optimize something in a very complex system
Yes! You're starting out well.
> If I'm running a business, and my payroll increases 30% while sales remain flat, I have two options: 1) slow or stop hiring, cut staff, or even go out of business;
Aaaaand... you crashed into the water. Raising wages increases productivity, demonstrably so: http://www.raisetheminimumwage...
Of course, as said, this only 'works' if the wage was abysmally low to begin with (which is true in this case). If you're already paying your workers $100/hr, paying them $200/hr is likely not to do much, but going from $5/hr to $10/hr is going to do a lot.
There are many reasons for this. Low-paid workers often lose productivity due to working multiple jobs or making non-optimal life decisions to save money. Employee theft and misbehavior goes down. Job satisfaction (and the resulting increase in productivity) goes up. There are a lot of other positive effects.
> I think it will largely end up being a feel-good measure that well-off, well-meaning people can use to congratulate themselves about
I actually agree with you a little bit here. But that's life.