The Time has a good and interesting article with some new scientific research about extending luxury brands.
In essence, it proofs the concept of f.e. Chanel moving into cosmetics decades ago:
Making a luxurious brand available to a wider audience with brand extensions into product categories, where less money per purchase is needed.
But there are traps along this way. Among many, if your brand extension does not support your luxurrious brand positioning by being too cheap or packaged poorly, your doing more damage then good.