I suspect its an older rate that he got and was able to lock in for a while.
The current rate is about $0.07/1000.
If $0.24/1000 is a "fuck off" rate, then Imgur is less than an order of magnitude more friendly to new developers. Imgur's price 4 years ago was $4k for 150M requests.
Reddits pricing is mostly in line with similar social network API pricing (Twitter is still an outlier).
Sounds to me like that rate might be Imgur saying "we welcome your business," rather than "fuck off."