This is probably not what you want, but setting up trade routes to supply your factories in the X series can be quite exhilarating.
If you make smart choices, and the goods at your factories are flying off of the shelves because there's solid demand, and then you set up a factory close by to take advantage of those higher end goods, and you rake in the cash....
It makes you feel like Sam Walton must have felt when Walmart took off.