Do you really believe that this team has the skills and knowledge to find these bugs and construct working exploits for them, but then don't understand the exploit market? Or, that they act against their own best economic interests?
Maybe they're just ethical by nature. If I could make lots of money by breaking the law or doing something un-ethical I (and in fact the vast majority of people) still wouldn't do it. Money isn't the only motivating factor.
So it is very well possible these exploits would have been worth more on the open market and still the team decided to work on this in a white-hat setting because they are simply good people.
If you consider just your own "best economic interest", a lot of "jobs" like drug dealing, prostitution, fraud etc. are good choices. Morals, not wanting to go to jail, and a concern for your own physical security are non-economic factors that make these bad choices in most people's view. Blackhat hacking falls pretty much in the same category; selling exploits may perhaps be technically legal, but I wouldn't bet my paycheck that you couldn't be put behind bars for aiding and abetting in a criminal offense or similar.
But building a reputation as brilliant whitehat surely confers significant economic benefits as well.