https://hackerone.com/slack?type=team
It says right on the tin what the payout is going to be. If you don't like the terms of the program, don't participate. It's not really that difficult a concept.
I assume that would be _one_ way to get companies to care more about rewarding people who spend substantial amounts of time researching their security
If someone doesn't like the terms of a particular bug bounty program, I would ask why they are doing research against that company to begin with. That's like someone really wanting kids dating a person that doesn't want kids and hoping they will change their mind after they see how awesome it will be. Almost without exception, if you read the comments from the individuals reporting the bugs, they will actually defend the status quo (as is the case here if you dig around). It's mostly just loud people in the vicinity of this trying to drive up the market.
Of course in my example I could try to incentivize said partner to have children by all sorts of unethical means, and there are certainly ways for researchers to try to incentivize corporations to increase bounty scope or payout by unethical means. This is generally considered 'extortion'.
Lastly I think it's also important to point out that legality has nothing to do with ethics, and I certainly believe there are cases where disclosure is warranted outside of any established paradigm of 'responsible disclosure' or bounty program.
My point was about the wider security economy. It feels like Slack are low balling for work which they have a moral duty (er, moral in the sense that spectres haunt Europe) to pay something more like a living / minimum wage for hackers.