How much does it Cost to play the games?

That's variable. All games can only be played with a power card. They very between 1.0 - 9.5 "tokens" or points off your power card. It depends on the games you play.

D&B hide the actual cost of each game by changing the monies to points. Newer games can be 16 points while older can be as little as 3 points. The fun and popular are 6.8 IIRC.

The points are sold in packages.

Also, the more points you buy at once, the less they cost, so that also affects the price/game.