Disk Utility reporting way TOO much disk space

I have an issue that's the opposite of what most people experience. Some have discovered all their "free space" has been eaten up by something invisible and no longer available. (Local time machine backups are a common culprit for that.)

My situation is the opposite. According to "About this Mac," Disk Utility and "Get Info" on my drive, I have nearly 750 GB available on my 1TB drive as seen here:

However, this is completely incorrect. What is shown here in the finder is correct:

In fact, I have well over 700 GB actually used out of 1TB. There's no way I have nearly 750 GB free!

Furthermore when examining storage from "About this Mac" it shows these values (all of which are incorrect):

For example, the above shows my documents as being 190 GB. But in the finder, my Documents folder is shown correctly at about 450 GB.

The usual advice is to have Spotlight reindex the entire drive. I've done that twice already, but to no avail. Both Disk Utility and Drive Genius cannot find anything wrong with the disk, yet they too report far too much free space. Something is obviously very wrong.

I cannot trust using my Mac in this condition. Any suggestions?