I think you're looking at the Enterprise domain controller pricing. the Standard size (up to 30,000 objects) is 12 cents/hour for two controllers.
$0.12 * 24 * 30 = $86.40/month.
$0.12 * 24 * 30 = $86.40/month.
I'd change the statement in my parent post, but I don't seem to be able to edit it.