Hanchi,
so I paid the green card fee on July 2nd, mother arrived here on August 14, and on September 2 the status on Uscis website changed to card production ordered, which makes it 60 days from the payment of the immigration fee. This past Friday, September 10, the card arrived in the mail. I hope this will give you all an idea as well. I hope your parents have gotten theirs too by now!