Something like: Wow, that's great! or Very well done! is good. We don't say 'you're so good'.. that sounds possibly sarcastic (like you think it's not good), maybe.. Actually, students say 'so' too much and incorrectly - you should say 'really' in most cases like that. It's really expensive/hot/difficult/good, etc :)

I think it would be more natural to say anything along these lines: I'm not surprised, you really deserve it! I can see why they gave you that scholarship! You earned it!