The terraforming process is a long one, spanning many centuries. During this time, science will not stand still. Many things we consider impossible will be made available to mankind, and many things not even dreamed of will be commonplace. One such thing might be anti-gravity:
Think about it. If anti-gravity were to become commonplace, it really would revolutionize everything. Hovering monuments, floating dog-walkers, and flying cars. Elevators, levitation trains, and cities in the clouds. And incredibly fast space craft.
To reflect this, you get a universal discount of 2, making every subsequent card cheaper. This will quickly get you your money back, and more! And on top of that, you also get a well-deserved bonus of 3 VP.
On the other hand, you may never be able to play the card, because it has the most difficult requirement in the game: you must accumulate 7 science tags before you are allowed to play Anti-Gravity Technology. That is more than you may encounter during the whole game, making this a bit of a gamble to buy. To go for it, you must buy the card for 3 megacredits, and then hold on to it in the hope of someday having 7 science tags. You will probably have to invest in science projects that might not really fit your strategy. And you will go into each research phase hoping, hoping that those lovely white tags will show up. Because if you can get Anti-Gravity going reasonably early, then it will all be worth it. Your opponents will groan as your discount starts to kick in, card after card after card. It’s a wonderful feeling.