Companies such as BMW, Audi, Mercedes, and Tiffany are thriving these days because they are expanding their

Question:

Companies such as BMW, Audi, Mercedes, and Tiffany are thriving these days because they are expanding their luxury brands into more affordable product lines, thus allowing them to offer their premium branded products to a wider audience. An example is Tiffany's $75 Heart Tag Charm, the $30,000 Mercedes CLA, and the Audi A3.
Required
What type of strategy (cost leadership or differentiation) is being followed by Tiffany, BMW, Audi, and Mercedes? Comment on how effective you think this strategy will be for these firms.