i find the business side really interesting too. and if she's really been able to get away with 40 years in the industry without thinking of the business side then she's extremely lucky. most designers don't have that luxury. for most ignoring the business side is a quick path to bankruptcy. plus, there's probably been somebody over at the label paying attention for most of its existence—the other half of the "couple" you mentioned, though it may not be a single person. a brand doesn't grow into something that size otherwise. maybe they're not telling rei what to design but obviously she's able to create whatever she wants because the money is there to do so. personally i'm more impressed with the designer who's able to successfully manage both creative and business.
I took the quote a bit differently. She's said in many other interviews that she takes the business side of things seriously. PLAY, as g transistor noted, is basically a money grab, and she's done collabs with H&M. I think her point was that her design process isn't focused on maximizing profits. The fashion world is mostly looking at trends, and often focuses on making clothes that flatter the body (this is esp true for women). Rei's work, on the other hand, is a lot more conceptual, and she creates silhouettes that are a lot more baggy and bulbous. In this way, her design world and the fashion/ business world are different.