This one might be what you are looking for if you want more clarity - it's absolute position on the leaderboard. So the groups 20th-1st get rewards for being in the top 20, and the group that is 21st doesn't. This could be combined with figures rather than a bar.
Eg
Group C .... 21st 4,235,091 balloons
Group B ... 20th 4,235,100 balloons
Group G ... 19th 4,235,203 balloons
It would mean that the group that came 21st would be annoyed that they lost out by 9 balloons, but at least it would be concrete.