Well, there will be a demo eventually, so you can always wait for that if you want. As others have said, there's no trading or exploring in the game just yet.
I will say though that I've thoroughly enjoyed the time I've spent with the game so far, and think it'd be worth $10 just for the alpha, which feels like a full game. The game is being continuously updated, and $10 is less than what the game is eventually going to cost. And remember, you're not just buying the game, you're also supporting the developers.