Image acquired from www.cafepress.com
"store" owner is James Macdonald, originator of Yog's Law
If interested in the T-shirt of like products go here:
Yog's Law - Money flows towards the author.
A mantra I have heard long and often as I have dipped my toes in the publishing industry, ran away, came back, researched the industry, had life, came back, attended cons, moved, came back ... Well, nigh on twenty or more years now.
It made sense, back before Amazon and eBooks, when the publishers ruled. At that time they paid for the marketing, covers, editing, everything. If a writer was paying an agent to "proofread" or a publisher "for marketing costs", a scam was occurring. James Macdonald became "radicalized" (his word) after talking to one poor new writer who fell for the scammers and likely lost everything. The story is here: https://www.sff.net/people/yog/. At the time Mr. Macdonald Message-board (yes, it is that old - when only message boards were the primary communication) name was Yog. Thus Yog's Law was born.
But publishing has changed in the last twenty, last ten, heck ... it changed from yesterday. A writer is often self-published until an agent or publisher gets interested. During this time the author is writer, marketing, and publisher. And while the writer should never pay, when the publisher's hat goes on money flows out for the cover art, editing, and marketing just like in the old days under big presses. An author may be able to cut corners if they know art, or website production, or any of a number of skills. But each time the author is working under a hat other than writing, they are not writing.
Having a press take 35-70% of the income from writing isn't bad when adding up the actual expenses of wearing the publisher's hat. In fact after the first successful publish, if an author continues to self-publish, I would recommend putting 75% aside from each royalty check until the next book and then use that portion as the "publisher expenses". That should cover all the overt expenses; there are still a lot of passive expenses, such as time not spent writing.
Excellent blogs to better understand the law can be found below:
Gail Z Martin - Magical Words - "Yog's Law---It's More of a Guideline" - 2/24/2016
John G. Hartness - Magical Words - "Making Money Mondays - Yog's Law" - 5/2/2016