Consider the value of the car with NAV when selling or trading in...

It's been my experience most used car buyers of higher end vehicles will want all the options and shop specifically for cars with leather, NAV, etc. If your car is worth an additional $750 w/nav package upon trade-in may be very worth it. Plus with more and more nav systems becoming standard and all the latest ipod integration gear out there I can't see not having the factory NAV in a brand new beemer