Here's a fun fact.
Let's say you love the 335i but are afraid of the cost compared to the cheaper 328i. Also, let's say you like having a moonroof, xenons, etc. Well, once you add the packages that allow you to have the same goodies that the 335i has as standard, well, you are now only 1-2K below the 335i in price.
So, if you really like the sound of the I6 and you enjoy xenons, surely you can say that the N55 engine is worth 1-2K.