think of the pool of money that is profit to go to workers. when employers make more money, more nominal amounts (not percentage) go to the workers collectively.

you can look at the balance sheet of basically any company to show this.

to contrast, I know of a single tech union, Kickstarter. From publicly available information I see no evidence that workers are getting more money. In fact kickstarter employees seem to be paid less than general (especially for NYC, where they're based).