I'm not a finance expert, but it may be because investment and purchase are are taxed differently (I don't know). You gave $100 away as investments, got $100 back as revenue. Meanwhile you establish that your product are worth $100 (while costing $80) and you have $100 worth of shares. Without considering side effects, you gave away $80 worth of product for $100 (supposed) worth of shares. But shares are subject to side effects and those side effects can be quite nice (making the news, establishing price,...).

The issue is that there's no organic force behind those changes and it makes everything hollow. You could create a market inside a deserted area and make it appear like a metropolis.