Database size - MDF too large?

Question

I'm maintaining a SQL Server 2005 database which hosts approximately 2.9Tb of data (2 x 1.45Tb - I have a RAW schema and an ANALYSIS schema so basically two copies of the data ingested). The recovery model is SIMPLE and the .ldf is at 6Gb.

For whatever reason, the .mdf is 7.5Tb. Now, there are only maybe 2-3 additional columns in ANALYSIS tables and not many NVARCHAR(MAX) columns which, from what I (may have mistakenly understood - please correct me if I'm wrong) may be causing additional space allocation. That's after shrinking the database just now - it was at ~9Tb prior to that. Any thoughts?

And, please, let me know if you have additional questions - I'm very new to database administration and optimization efforts (I usually don't do this side of the job :)).

Many thanks!

Andrija