I received an email from IDefense today. The email was an offer for the vulnerability I sent them a month or so ago. I was very happy to see the offer at $3000 US. This suprised me, as I was expecting an offer much lower. The vulnerability I sent them was not a code execution bug, and the previous vulnerability that they paid me for (which was code execution) resulted in an offer of $1500 US.
What happens now, is that I reply back to the email with a tagged subject line (including the word Accepted). They should then send me a contract (as a PDF). I will have to print out, sign, scan and then send back to IDefense.