We've purchased 3 Tesla vehicles since early 2013 - and purchased the extended warranty for all 3 because we expect to keep each vehicle for at least 80-100K miles.
Not only does the extended warranty provide you price protection from major repairs (such as MCU replacement), it also now includes Roadside Assistance and towing to the nearest Service Center.
The extended warranty for our 2012 S P85 didn't include towing - and when we broke down in the middle of Kansas and had to be towed to the KC Service Center, we had to make arrangements through our insurance company for towing. Now Tesla includes that with the warranty.
Another benefit of the warranty - if a problem does occur, Tesla may be willing to replace additional components related to a failure, if they aren't sure which component caused the failure. If you're paying for this a la carte, you'll likely want to fix only the failed component, which might save in part costs but could increase labor costs for increased diagnostic times. The failure in KC was with the front trunk lock assembly - at a Supercharger the front trunk latch popped open and could not be re-engaged, leaving the front trunk partially open - and unsafe to drive at highway speeds. Because of the potential risk of this recurring while we were driving on the highway, Tesla replaced every component related to the front trunk latch. Probably more parts than I would have been willing to purchase a la carte.
Extended warranties are insurance policies - some owners will save money, others will lose money.
For us, we're willing to take the risk on overspending on the warranty in exchange for the assurance that we won't overspend on repairs between 50-100K miles on the vehicles.