Microsoft Studios and developer Zoë Mode have altered the pricing of Powerstar Golf such that there's now a free demo-like base version of the game and content has been relegated to DLC packs. Your progress made here will transfer over if and when you add premium courses.
It's now possible to pay $19.99 (the original price) for all packs, or buy them individually at $5.99 a piece. Those are City Park, Emperor's Garden, Burning Sands, and Rocky Ridge. If you happen to already own Powerstar Golf, heads up: a bonus free pack, Coyote Canyon, is out today.
Actually, I'm a fan of this. It's a lower-risk way of getting into the game.