Actualy thats becuase, people who used to buy mehrans have either lost there buying power or opted for second hand vehicles, bigger and better then a brand new Mehran.
Incase of Corolla, corolla has atracted alot of market to it self, people who previsuly bot a Exi/Vti/Gli/Altis/Xi/Honda City, all have found the new GLi to be a complete car giving a bigger look, more durable, and a higher resale value.
By durable here i mean
Suzuki - 3 yrs
Honda - 5 yrs
Toyota - 7 yrs
A complete car i mean (power windows and central locking and Abs)
Liana doesnt count (as many people consider options City and Corolla these days . So lets not argue about Liana.)