Per their site:
"Example monthly cost:<p>If WebMD Answers was a TrueVault customer, their monthly charge would only be $1,604. Here's the breakdown: WebMD Answers has 5,036,000 questions, so that's 5,036,000 JSON documents stored . According to Alexa, they have 1,042,705 page views a month, so that's 1,042,705 requests. And presto, $504 + $1,100 = $1,604/mo."<p>To save money WebMD should store their json documents as compressed binary objects and get way more than 10k documents per $1.