Here is a screenshot of the bug. The regular price of “Sedan B” is $21,000, it is being discounted by 15% to $17,850 even though it is not missing any features. In fact, the “Sedan B”(udget) model has not been changed. Another model “Sedan M”(id Range) has been changed.
I think that the bug is related to your Video Blog 113 where you “optimized” the code for determining uninstalled features by storing a flag. That flag is being carried over from a previous model that was in the same spot. (I.e. previously there was a car in the same spot which did have a discount, but it sold and a new car moved to that spot and the flag was NOT set correctly after moving up 1 spot.)
Note, there is also a thread on steam which describes this bug as appearing in 1.80 – here is the thread: https://steamcommunity.com/app/591370/discussions/1/2733047810435188971/