I read about this game just this morning. The article was pointing out that while the game costs only $10 the game is based on micro-transactions if you want to have access to everything and the micro-transactions cost more than the game itself ($12 if you buy them all).
That's true. The first game, My Life as a King, did the same thing. It was $10 for the base game and then $1-$3 for additional content (each). Some of it (costumes) doesn't affect the game at all, but there are those things which make a big difference, such as additional races and new buildings.
I imagine there will be similar DLC in My Life as a Dark Lord.