In the World Government's adjustments of the bounties, it placed on 's Straw Hat Pirates, Nami's bounty is laughingly low. As a result, the World Government has unwittingly increased Luffy's chances of actually getting to Laugh Tale and thereby overcoming any possibility it may have to capture or kill him.
Bounties are used by the World Government, to not only announce who it believes are the most dangerous men and women on the high seas, but also to give the public an incentive to take out a bounty target without the need for the authorities to expend too much of their time, resources, or personnel. While they may seem a simple attempt to outsource work, a properly formed bounty can literally turn parents against their children. The World Government has used bounties to convince the world that a was, in fact, a devil with the knowledge, understanding, and desire to destroy the world. As a result, after the destruction of her home, Nico Robin spent the next 20 years fearing for her life as a result of the bounties put on her head.
By making Nami's bounty so low, relative to other members of the crew, told the world that she's not worth the effort to bring in. The bounty actually decreased the chances that she will ever be caught, or at least caught in the timeframe in which Luffy can reach Laugh Tale. But the reality is, in terms of physically reaching Laugh Tale, no member of the Straw Hats Pirates is more valuable than Nami. As the resident navigator, without her, it's unlikely that they would even be able to get out of Wano Country's "exclusive economic zone" let alone sail to an island that has only been reached by a handful of people in the history of the world.
In addition to her navigation, and cartography skills, a pirate crew can ever want, namely, she is attuned to the weather. As the result of her years of experience sailing the seas, she's developed a sailor's feeling of the "water, wind, and stars" that gives her preternatural ability to sense, storms, currents, and other seafaring information that is the difference between being lost at sea, and safely docked in port. This is the reason why Luffy trusts her in guiding him and the Straw Hats Pirates along the Grand Line. Indeed, there's a reasonable argument that when it comes to sailing, which occupies most of a pirate's life, Nami rather than Luffy is the "master and commander" of the Straw Hat Pirates.
By effectively stating that Nami is not a very valuable target, the World Government is given one of the most dangerous pirates in the world, a pass. While she to beat Kaido, or other top-level opponents. She has the ability to sail rings around him and the Marines. That is, she has the one skill, in the race to find Laugh Tale, which everyone needs to be successful, and that the World Government should target to eliminate now rather than later.