Depends on which way you approach it.
- If you're in front of a judge you would have to prove that this practice is NOT ethical. Say the manufacturer ripped you off with the casket you bought.
- If you're the reseller you would have to hide the fact that you are doing it or at least downplay it. Many businesses do it, they tempt you with sales (say a Chevy) and sell you at best a mediocre product (a Buick) while you can't afford the high-end (Cadillac) but they are all made by the same manufacturer (GM).
- If you don't like it you can choose to expose the practice in your word-of-mouth advertising and that is where the above comes in - how well did the manufacturer hide it and is it enough of an issue to be turned off by it.
There is a whole branch of economics and advertising that delves deeper into this issue and how to streamline the 3 products in order to achieve maximum revenue and brand recognition.