Doffy's portrayal in MF, PH and DR wasn't just for fun. He gets trashed on by losing to Bound Man but this was basically the debut of Gear Fourth - and it still means little since Doffy got mortally wounded by another Warlord whose DF is broken af. But, Hancock has a significantly lower bounty than Crocodile, while Buggy even took the whole fame, which shows yet again how strong Oda views Crocoboy.
Yeah. I mean a difference of 300 Million isn't that big if you are already in the billion range (like Queen having 300M more than Katakuri). Crocodile is part of an organisation that goes for the marines themselves and receives funding. Though yes, 1,9 is huge given he is just considered an associate and not the leader.
I think if Doffy came out, he would receive a bounty of around 2B. Maybe 2.1B. He was introduced as the Shichibukai with the highest bounty out of all the original Shichibukai bar Mihawk, whose original bounty was not displayed. Used a YC3 as a chair, broke out of Aokiji's ice and quite frankly wasn't bothered in the first place, attacked Fujitora and was confident being able to get rid of him.
So I too think people underestimate just how devastating Gamma Knife was, ripping Doffy's organs to shreds and having them further fried by Counter Shock. He was even seen later adjusting his organs again after Leo Bazooka.