True that here are a lot of replica and aftermarket wheels out there that look nice, but may be heavier and less durable than the OEM's. On the other hand some are better built and lighter. One thing I learned in my breif stint selling wheels many years ago is that like most things, you get what you pay for and there is no free lunch.
Based on the experience Car & Driver had with their long term 535i test car, not everyone thinks BMW's wheels are the most durable:
2011 BMW 535i Long-Term Road Test - Review - Car and Driver
By the way, another thumbs up on the Conti DWS's. IMHO best all season tire out there for the X5.