Why Nico Robin has the most undervalued bounty among the Straw Hats!

So I have been wondering for a while now on why Nico Robin doesn’t have an above 1 Billion Berries bounty and she only has a 130,000,000 Berries bounty.

1- Robin has a powerful devil fruit

2- She’s part of the “5th Yonkos” crew

3- She was involved with the Revolutionaries for two years.

4- She escaped Enies Lobby

5- She is the only person that can read the Poneglyphs which means:

-She can find out about the Void Century that the World Government is trying hard to hide;
-She can find where Laugh Tale is which is what the Marines don’t want.