If you have not finished the old cities, for example : New York, Cuba, Moscow and Bangkok.. it's the perfect time to do it!
Zynga has released the new feature of "Old City Bonus"!
If you do jobs in those cities, you will have double of mastery bonus and also double of cash.. Please check on the screenshots below..
I don't have screenshots for Cuba and Moscow, but I bet they belong to the old city..
But wait, I notice that not every player has this feature on their game!
I don't know why but... again, it's not fair, Zynga!
Don't know how to get it, when the feature being rolled out to every player, etc.. meanwhile, just enjoy it while it last..
PS : Thanks to George, Travis, Hayden, Gaspump, Linus, VaibhaV, Alwi, etc.. Thanks a lot, my friends!