Think about it this way. 35,000 copies at a major trade publishing house is respectable but nothing to issue press releases over. Although not every top author sells in the millions (and you'd be surprised how many books on bestseller lists only sell in the mid five-figures or slightly above), 35,000 books usually means "midlist," which is another word for "fine, but no guarantee of a publishing future." Depending on where you publish and what the book was, it's either just solid, so-so, or the dreaded kiss.
But at a university press that same 35k is just wonderful. Many UP books only sell a few hundred copies, so authors cracking 5,000, let alone breaking into the five figures, are stars. Of course the discussion may come back to money again (it usually does). It's true that literary advances (if they come at all) can be . . . well . . . "modest" is a polite way to put it. But there are ways to structure the contract so that you do well if the book sells. I have often observed that book sales and subsequent royalties are more under the author's control than most are prepared to admit anyway.
Go down the list of bestselling authors over the last twenty years, and you will find person after person who took exceptional responsibility for their own book promotions, their own speaking engagements, their own careers. Fluke bestsellers do happen, but the majority are more often the result of hard work and learning how the book business works. (Don't believe me? Then read John Bear's aspirationally titled The Number-One New York Times Bestseller. It's a roster of authors who made their own magic.) That "magic" can happen at a university press just as easily as it can at a trade house, since there is nothing stopping the book from breaking out from either source.
The Publishers Weekly article celebrates Yale University Press at 100. Who knew (I didn't) that it is the home both of the classics Life With Father (1936) and A Long Day's Journey Into Night (1956). Happy centennial!