http://yahoodevelopers.tumblr.com/post/62953984019/so-im-the...
(and HN discussion: https://news.ycombinator.com/item?id=6488897)
Bounty hunters do this stuff for a living. If the company pays with $25 vouchers and the black market pays on the order of tens/hundreds of thousands, who do you think "these people" will go to?
There are close to zero companies that pay tens/hundreds of thousands for a bug, and yet clearly bounties are being paid and not 100% of bugs end up on the black market.
Facebook has paid $12,500 for one (http://techcrunch.com/2013/09/02/security-researcher-discove...)
Google will pay up to $20,000 for one (http://www.google.com/about/appsecurity/reward-program/#rewa...)
Forbes even posted an article a couple years ago on the market of zero day exploits and listed prices someone could get for zero day exploits with prices in the tens/hundreds of thousands. (http://www.forbes.com/sites/andygreenberg/2012/03/23/shoppin...) It should be noted that they state in this article that the groups that will buy these exploits for these prices are generally western governments.
"Before releasing this information, Hall emailed Yahoo and tweeted at its engineering team and CEO Marissa Mayer.
It was confirmed to him that its servers had been infiltrated but Yahoo refused to pay him for alerting them as it was not part of the company’s bug bounty programme."
[1]: http://www.independent.co.uk/life-style/gadgets-and-tech/new...
EDIT: The quote previously included "Yahoo is notorious for its disregard of bug bounty hunters, having last year rewarded one such hacker who identified three bugs in Yahoo's servers with a $25 voucher for company merchandise." but I moved it here as it caused confusion regarding which issue the article was referencing.