Mamba: that's the general idea behind the rating system: you get more points if you beat higher rated players. higher rated players are (suposedly)harder to beat, so when you win a game against one, you get a bigger reward. Makes sense, no?
Also, if you are 400 points behind and win a game against a big player, you'll get more points then if you're ratings are similar.

Of course there are other factors like number of games played and I think the formula is different if it's an established rating or a provisional one. But the general idea is the same.