This is something I ask myself a lot (as someone focused 100% on open source at a company whose core business is not open source support).
For all the hype that open source has enjoyed as a business model, it is much smaller/untested/too early to tell compared to the proprietary model. The most financially successful open source company to date is Red Hat, which, at 10B USD+, is a great success by anyone's measure. But that's the best any open source pure play company has done. If you look in the other direction, Oracle is worth 180B USD, and even a fledgling BI company like Tableau is in the high single digit billion.
As much as I'd like open source companies to be an Oracle-grade blockbuster success, the brief story is not exactly promising.