Imad is correct you need to check that you are searching in Item rows.
You could find your controls in the following manner to determine the cause of the error:
Label lblKonutFiyat = e.Item.FindControl("lblKonutFiyat") as Label;
if (lblKonutFiyat != null)
{
lblKonutFiyat.Text = MyResource.lblKonutFiyat;
}
....
If your control is null it will gracefully handle it, any labels that aren't getting set will provide you with the problematic labels.