I've used and loved bitbucket for years for private project hosting, but for the occasion where I need to put more devs on a particular project I'm not sure why I would pay for it now over using gitlab for free. It might be different if it was 5 users per project for free, but 5 collaborators across all of my projects is just too limiting - especially when I can get everything bb has and more from gitlab.
At the same time I understand bb needs to make money - hopefully they'll make enough to keep up the competition.