It's easier to do this with a high level Group Appraisal super specialty where you can control the prices of the shops at will.

Using the Contraband super specialty, keep creating materials until you get Forged Bills, Checks, Stocks, Documents, etc. These can be sold at a really high amount if you Raise the price using the Group Appraisal super specialty. Use this trick to earn millions of fol early in the game.