You should be able to get an exact match from Batteries Plus, http://www.batteriesplus.com/p-36538...sli95r-li.aspx, for around $200 and install it yourself. The dealer is charging so much because they are probably selling you an AGM-type battery rather than basic Lead-Acid. My dealer said they are only selling the AGM-style anymore when I asked about mine several months ago. Also, they will charge you extra labor to "register" the battery. This topic is debated up and down the e60 chat rooms, and I decided not to do it. A battery is a battery is a battery, I feel.
2009 M6 Coupe, SMG
2004 545i Sport, 6 MT (Sold)