Looking at these discussions of what RPG corporations need to make to even consider they are profiting, makes me damn glad I'm a very small concern, and a sole proprietor. Like most 3PP, I'm a one-person show, who operates out of my own home, and though I also publish for 2 other authors besides myself, and have paid for artist contractors in the past, my operating costs are very low, considering I have no employees, and almost never any contractors. I pay monthly subscriptions to Adobe, and for the 3D programs I use to create illustrations, and the electric bill to pay for the operation of my computers - those are my only true expenses, aside from maintaining my computers, electronics equipment and software (replacement now and again, etc.). The only other investment I have in my work is "time", which I greatly value.
Unlike many 3PP, I'm a professional freelance illustrator, cartographer and graphic designer so I create all my own art. Art is a major expense for most small publishers, especially for cover art pieces and maps. So not only do I not have to contract my art, I can include boatloads of extra maps and other art content, that most publishers couldn't dream of affording and still have a profitable end product. I also do my own page layout. Advertising wise, I only do grass-roots, non-cost, posts to ENWorld, Paizo boards, Facebook and other social media, I don't pay for advertising ever. Although the many products I sell on DrivethruRPG provides points I can use to apply to banner ads on the website, which I've yet to cash in, after 15 years of doing that - so I do have another free form of advertising available that I can use.
About 5 years ago, I released Starships, Stations and Salvage Guide supplement for Starfinder co-written by myself and Edward Moyer. For 6 months it was the #1 Starfinder 3PP product being sold on DrivethruRPG. It's a "Silver" best seller on that platform still. Some products do great, some products less so, but on average I get decent sales on new products, and continuous sales on all products. I've got one map product, among many, that's a $2.00 costing 1880's steam train map set, over the past decade I've sold that one product 20,000 times. So I'm not a big guns publisher, but I am still successful. Definitely not what a corporate entity would consider profitable, but for me it's plenty profitable. I don't need to ever become a big publisher, as long as I continue at the level I am now, I am content, though always hope for growth in the future...