So you are not looking so much for the theoretical/technical end, but on the impact on society and economy, etc...? Is this some sort of an essay/commentary on RDMBs?
This is an interesting time to do this, with the death of the relational model's inventor E.F.Codd just a few weeks ago. There is a lot of discussion going in the business world these days about the impact of the relational model, and what its future is.
Here are some interesting links that might get you started:
Now, if you are looking for statistical information on the financial side of things, I wouldn't know where to start, but you might start by researching information about sales of DBMS systems by such companies as Oracle, IBM (DB2), Sybase, Microsoft (SQL Server), Interbase, Ingres, and a large collection of other database vendors.