I'd imagine this has been suggested before, and I haven't been here that long so what do I know
First Suggestion
Introduce a mid-end market for cars with a value of $50k to $100k, located in the centre of the city, potentially where Legion car park is. High-end's values would therefore change to $100k+ and would remain in the west.
Second Suggestion
Move low-end to somewhere where there's more going on as it seems to be pretty dead. Potentially somewhere in the east of the city.
By adopting the above approach, you'd have three places in the city to buy & trade used vehicles, and three different places to accommodate different budgets.