oh my god...where I do even start? These bounties are not "a security researcher" or amatuer people who decided to play with iOS and perhaps find a bug to report for money.
A security bug that Apple values 200K probably costs more than a million dollars (in damages) if used to for an attack on personal data or anything illegal. This is not like a root access thing for jailbreak devs to try and find exploit for kernel.(these also cost some money and some ex-jailbreak devs were credited in security patch notes by Apple). We are talking about major things that can be sold, like WannaCry virus that was probably sold and activated because NSA did not report to companies about the potentially deadly exploit.
I have a very close internet-friendship with several developers as well as some hackers from across the world. And trust me when I say this, most hackers or devs who find exploits are in it for the money, for the highest bidder. There are so many morally bankrupt people in the dark web world that you would never believe.
A small secret for you: I talked with Cydia creator, Jay Freeman (saurik), and he told me that recently he got so many security reports on jailbroken iPhones that he personally wants to kill his own creation. (just google "Jailbreak is dead" and you'll find official public statements, not what I said)
All I hear is a lot of blah blah blah, from a community I know too well, of self serving mercenaries.
Almost all the NSA exploits were likely horded not only by the NSA, but by many foreign governments,
companies doing industrial espionage, dozens of different groups on the Internet of dubious motives, and your so called "security researchers". For each one you know about, there are 2-3 you don't know yet. Most are not thankfully severe though they can be if they can be chained.
I've got 30 years of computer engineering behind me and dealt with security for a hell of big part of that
I know what I'm talking about. I've been in contact with god damn lot of this crowd on both sides of the fence
(cause you have to befriend them, to beat them sometimes...) at various levels since the mid 1980s
when I first touched a Unix system.
What's to tell me they don't sell those exploits to many different people and then 1-2 months later report them
just as their value is about to go down (because eventually if enough people know about an exploit, it will get back to Apple or Microsoft) and double or Tripple dip.
I consider many of those people CROOKS and even BLACKMAILERS.
That's what my experience has taught me.
Apple's bounty is not targetted at most of these folks because they are not to be trusted.
There is no amount of money that will be high enough to make them trustworthy: this ship has sailed.
It is targetted at the smaller group that has a conscience and that believe they should be compensated fairly for their effort, but not more. It's possible that the current compensation is not seen as fair for those people's effort; but, that's has nothing to do with paying millions for bugs.