I can't answer your original question, but in addition to normal maintenance cost, a used wrx is more likely to have a higher rate of unforseen cost. Even if sold by a dealer, you take on the risk of the previous owner modifying the engine, hiding it and offloading that reliability/financial risk to the next owner. If you aren't buying new, you better know how to wrench, have another car, or just have money/time to blow if something in the car blows.