$12,000 per 50 million requests, which, for an app like Apollo comes out to around $20 million/year. Apollo currently charges for a Pro version which is $13/year. There are about 50,000 subscribers - so Apollo makes around $650,000/year. For comparison, Imgur comes out to about $3000 per 50 million requests - or 1/4 the price of Reddit. Reddit's API pricing is more comparable to Twitter, and Twitter's decision to start charging API access had less to do with money and more about shutting down 3rd party apps. Reddit seems to be taking the same approach - instead of just saying they no longer want 3rd party apps, their eliminating them in the guise of charged API access.
If you're truly interested in the details of all of this, you can read Christian Selig's (creator of Apollo) Reddit post breaking down all of the issues with Reddit's API pricing:
Again, the issue is NOT that Reddit wants to charge for API access. Again, if you really want to know what is going on, just do a quick Google search and you'll find tons of articles detailing the issues. One of the common themes, however, is that both users and developers have no issue with Reddit wanting to charger for API access. If anything, most everyone agrees that Reddit needs to do something to become profitable - whether that is charging for API access or allowing/requiring 3rd party apps to show Reddit ads. Which directly leads to my next point: instead of or in addition to, Reddit could have relatively easily changed how their API works to allow Reddit ads to be displayed in 3rd party apps. This is a suggestion many, many, many people have made. Ads are Reddit's primary source of income, and their biggest issue with 3rd party apps is that they don't display Reddit's ads, by providing ad access via their API this would have basically solved their issues.
Furthermore, Reddit has been extremely opaque in this entire saga. They announced they were going to start charging for API access months ago, but then didn't announce the actually pricing until a couple of weeks ago, giving developers barely 30 days to make the necessary changes to their apps - which simply isn't enough time for the vast majority of independent app creators. In addition, developers have been attempting to work with Reddit since the first announcement, but often times have been met with radio silence.
Again, if you are truly interested in all of this, I suggest you do some research on your own to educate yourself on what is actually happening.