But collective bargaining is giving up freedom to get more negotiating power. The union prevents its members from, e.g., working more than a certain number of

But collective bargaining is giving up freedom to get more negotiating power. The union prevents its members from, e.g., working more than a certain number of hours; without that restriction, the members find themselves compelled to do so. Of course, the restriction couldn't exist without the union -- that you have a lot of people acting in concert here is important (since otherwise the restriction couldn't be enforced, and more imporantly for these purposes, would be seen as unenforceable). So in that sense it's not like the case where you deliberately break a machine you own to prevent yourself from having to use it. But both cases make use of this principle.