As a point of reference, here are some sizes for the repos of the game I work on which has been developed over around 11 years.

120 GB for the game data repo. This is the repo for the source and art that actually ships.

2.5 TB for the raw art repo. This is where the pre-export raw files go.

Obviously it would be impractical to require that the artists all have the entire repo. We use SVN.