The same logic probably won’t be applied to the Marines since killing Akainu wouldn’t actually end the organization, because another Admiral would be elected FA. The FA isn’t the real leader, they work under Kong, who works under the Gorosei, HK, and IMU. The gap probably won’t be as big between Akainu and the other Admirals. I could see 3.5-4Bil, but not 5bil.
5bil+ will be saved for Kong, Gorosei, or HK leader if we ever see CG place bounties on them.