For the record, this solution only passes about 50% of the time :(

I agree with you. Just added a statement to the text of this kata.

From the current description, it's very clear that at year 3 and after the car depreciates 10% per year. I am marking this as resolved.

Yeah, this part does not make any logical sense.

Try submitting again. I had the same issue (I still think that this kata would be better off asking to round the result to a certain number of digits), re-submitting again helped, since some of the tests are random.

Sorry, but "you should have enough information to try the Kata" is not even close to being true. Granted, I am new to JS, but level 7 Kata is supposed to be relatively easy to figure out with the information provided and some extra search. This is so not the case here! I've spent at least a few hours reading about prototypes and trying everything I could find. I am nowhere close to solving this. Either it's been mismarked at being level 7, or the description is misleading and confusing. Or you're asking for something that's bad practice and is only a disservice to the beginners. I'm very upset with this Kata. Spent so much time and frustration and haven't learned anything useful so far.