What drives our economy? Scarcity. What's the long term effect of capitalism? Commoditization, i.e. driving the costs down. Some people view open source as being about a post-scarcity economy in which human labor isn't need, an economy based on abundance. That's bullshit though. Open source is about commoditizing software developers in order to increase profits.
So the answer to your question is that there are only 2 ways to commoditize open-source:
1. make it a complementary to something proprietary and sell that instead; the "open core" model is known to work well for some companies
2. choose a restrictive license to make it useless for the target audience (e.g. GPL / AGPL for libraries)
You'll notice that I'm not mentioning selling support. Some consultants earned their name by contributing to open-source. But you can also write books, or blogs and you'd probably earn a bigger following. And you're still selling your own personal time, which is limited, as there are only 24 hours in a day, you're probably not a rockstar to have obscene hourly rates and if you're thinking of building a company around supporting open source, just don't, as you're not Red Hat and you'll never be.