Basically, the reasons for high car prices (both used and new) come down to 4 basic things in Pakistan
Locally assembled not manufactured (all high-tech things are imported). Only Mehran has a good quantity of localization but even it does not include the priciest things - chasis, engine, and transmission.
Economies of scales (or the lack thereof). Since the Pakistani market is small, and our auto-part suppliers are neither high-tech nor competitive enough to export, parts manufacturing costs more in Pakistan than in some other countries. This adds to the overall cost of the car.
Duties and taxes. We levy a flat sales tax on everything produced and also have hefty import duties. This causes a compounded effect since the GST is compounded over several phases of a product being manufactured. For instance, those mining or importing raw material will pay tax which is added to its sale price. The raw material is bought by the first vendor who converts it into steel and pays tax on the combined cost of the raw material, the tax paid by the importer, and the value added by the vendor. When this vendor sells his stell to a second vendor, it already contains two taxes. The second vendor gets the steel and converts it into smaller parts and pays tax on top of the initial two prices including two taxes before selling it to whole-part producer who again pays the tax on the compounded prices.
Triopoly. With only 3 major manufacturers with little competition, the profit margins are kept high. In some cases, such as PakSuzuki, there is virtually no competition at all. Hence, prices tend to be high.
Only Mehran and Corolla have a high level of localization and significant sales. But they too import crucial components and their vendors also import parts, thus getting affected by rising dollar/yen rates. Prices of Suzuki and Honda City are lower in India because they sell significantly more there. Otherwise, the price of Corolla in Pakistan is less than regional countries.
In many cases, the companies are not operating on full capacity which further increases prices. For instance, till 2016, Honda was operating on half of its installed 50,000 units per year. This means fixed costs amortized over the number of vehicles add significantly to the price. If 75000 to 100,000 units of the same model is produced every year, it will significantly reduce prices.
