Your net worth is the sum of the values of all your assets combined.
(The value may take a few minutes to update.)
This includes:

The moment you start to spend currency on one of these things, the value will be added to your networth.
An example:

  1. You have started a new game and built your first greenhouse. There is also a small transporter in your greenhouse.
  2. The greenhouse is worth 20,000 bucks, and the small transporter is worth 15,000 bucks.
    -> Your net worth is 20,000 + 15,000 = 35,000 bucks
  3. Now you open a production line and start an upgrade for 4,000 bucks.
    -> Your net worth has now increased to 39,000 bucks.