The possible ways: Migrate file shares to SharePoint 2010
Now your client wants you to suggest something for the 50 GB contents which is lying on the file system. Users are fine with that and they don’t want SharePoint or your client will be more then happy to see these 50 GB contents in SharePoint and enforce users to follow WCM standards by leveraging SharePoint.
Option 1: You can simply set up SharePoint and let users slowly migrate to it while supporting file shares at the same time.
Option 2: By creating sites and using the Page Viewer Web Part, the team members can both access the SharePoint site for collaboration and access the read-only file shares. The good thing about this approach is, it feels like you are in SharePoint and using it’s security model. Though it’s correct and another good thing is, if you have imposed any security on your file system contents, it will follow that. J
Option3: Get a third-party tool like Quest Software's File Migrator for SharePoint, AvePoint's DocAve File System Migrator for SharePoint, and Metalogix's FileShare Migration Manager for SharePoint.
You can then decide how you want to proceed. If your client is good to spend few thousand dollars buy a tool and do it or force users to adopt new platform or let them be there on file system and feel them like they are in SharePoint.