People don't understand bounties.
Bounty has nothing to do with strength, but due to Pirate activity whether directly against the WG or indirectly.
By direct, if you attack the WG directly or do anything illegal, they consider it a threat and will give you a bounty.
By indirect, I mean if you attack anyone whether it's an Emperor or a Pirate and do something significant enough to make the news, said character will gain a bounty even if it wasn't done against the WG.
Bounty rises to reflect the magnitude of all the crimes and pirate activity a character has committed.
The more activity a Pirate is involved in that makes the news, the more likely they are to get a bounty increase.
Burgess only had a 20 million beri bounty pre-skip despite being a Haki user; Nami was 16m and Brook was 30m and neither of these characters are stronger than Burgess. Why then are their bounties so close to each other? it's becasue the crimes they've committed and the activity they've been involved in outweigh whatever Burgess has been involved in, not because they're stronger.
Luffy had a bounty of 300m at Marineford; Squardo who was a Haki user, powerful enough to defeat Pacifista alone and able to even somewhat defend himself against Akainu and stab Whitebeard... he had a bounty of around 200m. Is Luffy at Marineford stronger than Squardo whom Whitebeard entrusted to comandeer his fleet in his stead? No, it's just:
- Luffy commits all the big crimes and is involved in all the big pirate activities that make the news. That's why he had a higher bounty than people far superior to him.
Why aren't many characters possessing bounties higher than Luffy? It's because not many of them are crazy enough to fight Shichibukai, break into Impel Down, hit Celestial Dragons, etc. This is why they're known as the worst generation.
- Take Katakuri's bounty of 1 billion. He's literally 50 years old. Been a Pirate since maybe the age of 20? So, 30 years of Piracy and 1 billion bounty meaning his bounty goes up 33 million a year.
- Luffy, Pirate for a year and earned has an average of 300m beri increase per year.
- Ace, Bounty of 550m, Pirate for 3 years, increase of 166m beri increase per year.
These guys bounty averages are higher than Katakuri's. Kata is likely been a Pirate for 30 years, so it's not like his 1 billion bounty happened in 1 day, it took years.
A bounty looking small doesn't make it small. It's why Urouge even with a 108m bounty is considered as a part of the worst generation or a supernova. Anyone who can accumulate a bounty in the 100s in just a year? That's significant because there are many pirates who have just 200-300m bounties despite being Pirates for decades.
Oven and Daifuku only have 300m bounties, are in their 50s for the most part and have been Pirates for decades, so maybe a 10m beri increase a year?
Blackbeard had 0 bounty even as a WB Pirate because he didn't stand out. In just what, 2 years, a 2 billion beri bounty? That's insane. An increase of 1 billion a year on average when Katakuri's took what, 30 years to get a billion? Not necessarily because there's a strength difference, but crimes and pirate acitivty.
Big Mom and Kaido, 4 billion beri bounties and have been relevant for what, 30-40 years? Took them 30-40 years to get 4 billion, so 10-15 million on average per year.
There's more to bounty than strength, while it does to a low degree, what raises bounty is activity and crime.
Every time Luffy's bounty has gone up, it's only after he's done something:
- Went to 30m after East Blue saga.
- Went up to 100m after Crocodile.
- Went up to 300m after Enies Lobby.
- Went up to 400 after Sabaody, Impel Down and Marineford.
- Went up to 500 after Dressrosa.
Without a crime or significant pirate activity, there's no bounty increase. It's not necessarily for defeating. Nami got a 50m increase at Dressrosa despite the fact she defeated no one, but simply because she was part of a huge crime/incident/Pirate activity.
So, when a bounty goes up, the value doesn't necessarily mean stronger, just means more activity.
Could be the strongest Pirate in the world and have a low bounty simply because he/she hasn't committed any major crimes or been part of any huge incidents that made the news. Burgess bounty was just 20m pre-skip, but Luffy's, Kid, and co were 300m in bounty. He'd easily have defeated them single-handedly at that point in time.