Think its easy to get that the WG have taken the three leaders of the Alliance and divided the Emperors bounties for them.
Bet that Teach have done something to make his bounty go to over 5b, and probably Buggy also have a bounty over 3b.
Also we knew the Emperor thing isnt something the WG control, its more like public opnion thing based on a mix of power and influence. And both Law and Kid dont have any influence, while both Luffy and Buggy seems to have a lot.
Of course there's the point of the WG trying to downplay Luffy and put he as equal to the other two to keep the JoyBoy thing low, but dont think the equal bounties are mostly because of this.