ClearCase is not cheap. However, it has global support behind it. Generally, once you have "enough" floating licenses, you can support far more developers than you have licenses for, especially if you set up global license servers.

At my site, at the time, 60 licenses were more than enough for over 200 users.

Go with a SaaS if you're able and use a vendor like CloudOne.

This is a very expensive product.

IBM Rational ClearCase, like any other IBM tool, is expensive.