It usually means "I approve of the fact that you did or said X".
Usually, "X" involves "standing up for your own interests", or "doing something brave", or "saying something unexpected".
For instance, if another member made a sarcastic reply to your post, and you answered with a crushing witticism, I might say "Good for you, '49!"
Or if someone at work asked you to make a false entry in the company accounts, for tax purposes, and you refused, I might say "Good for you, '49!"
It can also be used sarcastically. That might be the case in your "wages" example (where it would probably cause a great deal of offence).
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