Perforce SOFTWARE is free for teams as long as you stay under the 5 user limit. However, the hosting of that software, is entirely up to you. You’d have to setup the perforce server software on a server where all your team can reach (and those have various price plans depending on required storage).
That said, I’ve worked on multiple TB sized perforce projects and Perforce is fine with it. It’s more how good are you at organizing that much data and keeping the underlying hardware with enough storage.