The answer is to make a good product that can compete, (including monetarily) with all other similar products on the market. Almost no one in their own sane mind would prefer to spend more on a product with poorer qualities compared to other, unless they’re forced to.
Unfortunately, majority of the folks don’t value the FOSSness of a product and are not ready to pay for it for the sake of it, and it is totally understandable. FOSSness doesn’t provide additional functionality or feel, rather it is a message, a statement, an idea, a testament of trustworthiness and dedication. But it isn’t worth much if the product doesn’t satisfy the needs of users.
And the devs are very hesitant about making good, robust and competitive FOSS products, because these, much like usual closed-source, need many initial investments, but without a guarantee of payback and reliable business model.
There are successful FOSS products, but the FOSSness is not their main asset.
That’s the reality of the free market economy. If you don’t present something valuable, people don’t pay you. FOSSness alone is not enough. The way to a successful business model for FOSS products is to make people value FOSSness and it’s ideas. The way to make people value FOSSness is to advocate for it.