Also something that needs to be noted, you don't need the same original numbers of people in your kingdom to make equivalent money.

When you're making commerce in someone's fief, they will demand tribute as well. In the confines of your own kingdom, all the ad dollars are yours.

Which also means you don't need to chase the same amounts of people to make similar coin, especially if the deals you make with advertisers are between you and the advertiser (not you, the advertiser, and the king of some other fief).