Yes, Karachi registered cars have a hard time selling in Lahore/Islamabad/Rawalpindi and KPK and value also drops significantly when people see the peeli rang ki plate. Note that in Karachi, cars are a tiny bit cheaper as well compared to other cities even if it's Karachi registered. Try to sell in Lahore for the price you want it, lower it a bit after a while to a price which you find reasonable, if no luck, then try Karachi.
