Well that's a different story. I thought he was saying 10k from day 0 to day 30. I get 7k - 9k per month with follow - unfollow cycles on engaged/followers of usernames, liking, dynamic hashtags and engagement groups here and there when I feel that the content has potential.
You just have to found some nice follow back targets. I've tested over 20 targets with results from 15% to 66% average follow back.
There is no secret, if you have enough targets just decrease the followers/following limits of the followed/liked username and reduce the time that passed since their engagement with a certain account.