Because its ultimately cheaper to suppress unions than it is to pay the workers the fair salary.
I wonder if that's actually true - unionbusting is mostly an emotional issue for leaders and owners so I wonder if there's any calculation involved.
I've seen corporate HR got to insane (illegal) lengths to "stick it" to people trying to unionize - to the point of being severely fined.
So I wonder if anyone actually calculated financials here.
1.5bn is a drop in the bucket.
It's cheaper to try and block other workers from getting a union card in your union to limit supply than trying to up your skills, as well.
I'm generally pro-union and certainly fair wage, but it's important to keep in mind that unions will grow into their own power centers and have leadership with its own internal goals which are not aligned with either their working members nor the employers.