I have been looking online for extended warranty options and I found the attached documents which may help you with the pricing of extended warranty and maintenance plan upgrade options.
MPU is Maintenance Plan Upgrade and EVP is Extended Vehicle Protection. The car category list is in the MPU pricing file, here is a snapshot showing the 3 series list:
Extended Warranty Prices:
These are from one of the BMW dealership's website. They are generous enough to show the dealer pricing on the extended service agreements (MPU pricing file), they have a $750 margin on each plan.
I'm also attaching some sample plan contracts with detailed information on coverage.