When you use flairs, people that see them might not be particularly familiar with the meaning of badges, and whether "280k reputation is a lot or it's a mediocre thing".
So, I think it's appropriate to add some ranking information there - for example the one recently added to the profile "Top X % this quarter". Perhaps include the month and all-time data. Or even a a non-percentage rank for the top 500 users (ranked 89).
Another thing might be to add tag-relevant ranking. For example: "Ranked 5th in C#".
That's a lot of information to fit in the small flair, so the most relevant should be picked.
Update: This StackUser app was suggested, but unfortunately it does not display up-to-date information (30k difference with my actual reputation)