You ask the perennial question.
How do you make a million in [photography]? Start with two million.
What's the difference between a [photographer] and a pizza? A pizza feeds a family of four.

I'm not an expert. I've sold a few prints, but not nearly enough. I am working hard on this question. I think the first step to success is being lucky. Unfortunately I've never been one to be called lucky. I have not personally found an online service or site to be particularly helpful in sales or marketing as a nobody. I have to wonder how Jeff, above, sells anything on that site at all, much less thousands of dollars a year. I'm not seeing it.

I am trying to market towards uniqueness of the process (b&w silver prints) so "print-on-demand" services are not in my wheelhouse, but perhaps it is something to consider for auxiliary sales. Perhaps Jeff can enlighten us as to how it happens he sells that much and of what images. I am seeing a lot of highly processed digital HDR images that, for me, are frankly anathema.