Buy orders are first-come-first-served. If you put in a buy order now at 300 MoF each you still have to wait for the roughly 250k worth of older buy orders to be fulfilled before it’s your turn. And that can take several weeks.
The reason you don’t “see” aurum being sold is that the active buy orders exceed the amount of aurum being sold. And aurum put up for sale is automatically snatched up by existing buy orders.
First-come-first-served, as I said, i.e. oldest buy orders get fulfilled first. If you repost your buy orders every day then you will be in fact waiting forever. Otherwise it just takes a bit of patience.
I just collected some aurum this week, so people are still selling.
I’ve put some MoF on the exchange during the first days of the anniversary event back at the beginning of August. I got the Aurum at the end of August, so about a month’s turn around. But please keep in mind that big event drag many players back in for the duration. So if you put MoF on the exchange last week, you should have it by the time Halloween comes around, or during the event itself, since it’s the next big thing on the horizon.
Be patient, it will come around! But do not put it out to change your offer, or you’ll end up back at the end of the line.