I'm using Unity and I don't need the Pro licence at this point. It's still cool that they do that, but the true prize here is to learn, have fun and have people giving you feedbacks about your creation.
That's what I was going to say, if we want to create a game to win a prize, I think that the best way to do this is to create a game to sell it to players.
In my opinion, winning a prize in a Game Jam is just a bonus, but the first prize is to have the opportunity to make a game, to be proud of what you've done and to learn a lot. Having some new contacts, having fun (even if it's not always funny to spend time to do something which is not working / not as you thought).
Having prizes "Unity-oriented" is not something which is bad for me, they wants to create an event, Unity replied that they were gonna support it, it's just a good thing.
You can't have a prize which is going to be really cool for everyone, a pixel editor software licence ? What if I'm making 3D games without any pixel art ? A game engine licence ? What if I don't want to use it or if I've already got this licence ? etc.
Just be proud of what you're doing, Maybe you'll be good enough to win a prize, then if you don't want to use it, try to find a friend or someone who needs it, you'll make someone's day. :)
Have fun /all ! :D