2018 BMW i3.
Cost: free
Profit: $4k
Long story short, got an awesome deal on it, but I started having problems. BMW offered to buy it back but I refused. I loved the car and I wanted it fixed. I also told them I wasn't sure I would get the same deal since it was a unicorn deal ($204/mo after taxes on a 30 month lease). They offered a cash payout plus guaranteed BMWFS rebate if I got another i3, which I was planning to anyway since I really did love the car.
All in all, the settlement recouped all my expenses on the car. I basically drove the car for free for a year, including insurance, and I still had $4k in extra cash. I ended up finding a newer i3 with more options, upgraded interior and a bigger discount than my old one with a lower monthly payment ($194/mo).
My free i3:
20190310 - i3 Parking - IMG_1148-Edit_100 by
JMG, on Flickr