With the recent death of HDDVD, Microsoft's add-on drive for the Xbox 360 has now dropped to a scant $50, which includes six free movies. And hey, if you don't need the HDDVD drive (cause who does, anymore), they nicely point out
Provides an additional USB port for your Xbox 360 and includes USB 2.0 cable
So, there you have it - for just $50, you too can get an extra USB port for your Xbox 360. And a USB cable.
The historic HDDVD drive is just there for the ride.