"…on average, new product development projects with high emphasis on experiential design will result in 9% better financial performance than those which have only medium emphasis on experiential design. Similarly, products with high emphasis on functional design will have on average 10% better financial performance … When taken together … product financial performance will be about 20% better than that of a project with medium emphasis on both."
Bottom, line, a business's bottom line can be affected by the design quality. Not only that, but the freer rein given to a designer, the better the result.
Download the report in English-language PDF here.
(Of course, design is more than the bottom line, too. Design works on other levels too. Holding the Aladdin Sane cover in my hands aged about 12 changed my world almost as much as the music the package contained. Though only "almost". It may have helped increase sales, but its effect on me was more than that.)
Addendum. Of course, not all design increases sales. Or indeed is even "good": when design goes wrong (in this case "fashion" and an iPad accessory).