I think bounties would have something to do with how dangerous they are in general. As Jack puts it, he loves destruction and would rather run rampage as opposed to listening to reason. Big Mom's crew at least could see value in negotiating and making deals so as not to destroy (even if Big Mom herself was hesitant).
I would say his Billion bounty has as much to do with him destroying everything he comes across like a drought than just his pure strength. The same way Captain Kid had a higher bounty than Luffy, he caused more destruction on his way and thus the Navy would put a higher bounty on him to try get him taken out.
Thought I have no doubt that Jack will make a come back next chapter and be shown to be more powerful.
I love this chapter but it is infuriating that it is taking its sweet time to show what happened. Damn you Oda sensei and your damn world building. :P