When I add up all the major SaaS apps an average user has: SSO, Email, Chat, Storage, Zoom, Support. Combined, GitLab Ultimate costs 2-3x that. And I promise you that as much as we all hate a messy inbox, email is more broadly useful than GitLab.
The other problem with ultimate is that it strongly incentives you to NOT let anyone else on the platform. At $1200/year there is no way in heck I'm letting the artists use Git, they can stick to their terribly Dropbox hacks. Marketing team working on assets with developers? Use email, no way you're getting access to GitLab. The $100/user/month model makes sense if they are a core developer (still too expensive, but makes sense) using every single feature in the system, but nothing else.