Mozilla should probably add 'charging for revocation' to their list of problematic practices (required to be included in Firefox). Not that revocating compromised certificates isn't already required, but just that some behavior by poor CAs needs to be explicitly pointed out: https://wiki.mozilla.org/CA:Problematic_Practices
Good question. Maybe you can skip the fee by posting your private key to pastebin and send them the link? :P Might not leave you with an account in good standing with them though ;)
