You assume that we bought the car new, though.Yes, before you get a $5k discount off the purchase price.
That leaves a $5k difference, assuming zero interest earned on the $5k up front (which isn't unreasonable in todays money market).
Great CSI work!Based on when I started making BAP payments, and knowing that the battery buy out price drops 1% per month after the 5-year mark (confirmed this several times with MBFS), if I buy the pack out just before the lease ends I'll have paid (using $85/mo as the basis for BAP payment) $7565 since 5/2015 and will pay around $2400 to keep whatever (original or new) pack is in my car. That works out to just under $10k. So no matter what, it's half the price of a new pack.