I agree with the first two sentences of your post. But I'm not convinced that corporations in general are colluding to drive down the cost of labor any more than anybody who needs to purchase labor. It's natural to seek out good value, so it's not inherently evil to want to find the right skills at the best price. The real reason unions exist is to monopolize the labor supply, so that an artificially high cost can be maintained. I don't really have a problem with that if they can get away with it, but in the long view it serves to make our country a much less competitive place in which to do business.
Being competitive dictates that that will never happen. And your use of the phrase "artificially high" is wholly subjective and an opinion that seems to me to be rather difficult to defend.
Balance is the operative word in all (with exceptions of course) contract negotiations between union and management, of which there are too many shining examples to enumerate whereby companies make a decent profit and their unionized workers make a decent living wage. That of course can only exist if management sees their employees as vital assets to be dealt with fairly and if employees see the company they work for as vital to their job security and future prosperity. That precise example exists all over our country with or without having unions being involved, as some of those companies are so conscientious toward their workers that there is absolutely no need for unions to be involved, while other companies acquire parity between workers and management because unions
are involved.
If government, especially a gov't that got corrupted by those who seek to tip the balance that existed between corporate profit and equitable workforce compensation in favor of higher profit, which is exactly what RTW laws do, then I would agree with you that there then exists an artificial component in the relationship between labor and management, but it's entirely in management's favor.
This is heavy-handed government intervention in the affairs of business at it's worst. Something that conservatives regularly rail against, yet seem perfectly fine with when higher corporate profits are prioritized over the welfare of the workers that are an obviously essential factor in the success or failure of any business, especially where a large workforce is involved.
And from my experience, management will always have the upper hand in any contract negotiations with their workers via their ability to dictate company policies, agenda and goals.