Member of a union here -- two, in fact! -- in unrelated industries. "1.5x for overtime, 2x for 7th day" is pretty standard. If they were hourly employees and not getting a deal similar to this before, they were getting ripped off.
Mandated 1.5x overtime has consequences.
Another side effect (that I know happens in manufacturing jobs) is that people will deliberately slow their work during the week to work overtime on the weekend. I'd wager this is very common in jobs with frequent overtime opportunities.
What kind of widget are we building where underemployed meth-heads get to show up for as long as they want and set their own pay schedules? Nothing in life works like this.
Look at it this way: Why would you hire someone who doesn't think they're worth market rate?