$50k is 335i money instead of 328i, more features are standard on a 335i as well too
Sadly not currently true. With the redesign of the 328's including a turbo, 8 speed auto, and 240+hp they're so close to the current-gen 335 that if I were in the market for a replacement DD I'd rather take the 328 M-sport over a 335 M-sport (difference of $50k to $60k - so $10,000).
The reality is until the next redesign of the 335, that extra 50 HP isn't really worth 10k. I personally view anyone buying a modern 335 over a 328 to be grossly misinformed.
Disclaimer: My DD is a 2012 335xi with M-sport and the factory chip (I like my warranty and will consider a juice box after it expires) putting it at 338hp/347ft/lb. I'd still take a 328 M-sport over the 335 M-sport today given the choice.
Edit: Okay, full disclosure, I'd take the 328 today - but in six months I'd take the ATS-V in a heartbeat, for less than either BMW option. Looking forward to the ATS-V replacing my DD. Can't do the CTS-V, it's just too big and not a practical DD when dealing with the parking garages at work, and I have a Model S for the weekend/roadtrip warrior.