According to Bicycle Retailer and Industry News the new Shimano Di-2 (9070 group) electronic shifting will set you back only $4,139 for a single bike.
It will be 25 grams lighter than the mechanical version with in-the-seatpost 'optional' battery setup.
The mechanical 9000 Di-2 version goes for a bit less at $2,695 . . . a price that'll let you buy some flowers for the stoker to appease her!