I don't think a husband market happens in MGE. The closest thing you get to it are prisoners of war that a mamono can choose to marry, but actual slavery isn't something mamono do. Calling their husband "slave" is merely a nickname, they're not actual slaves.
Dark elves are not cruel by definition. They are catering to a BDSM fetish and they don't even inflict pain. The profiles are written by an in-universe author with an Order upbringing and thus there's alot of hyperbole that make them out in a bad light.
Now, if there were willing single men, then there could maybe me something like a "show" where mamono can call out to the man they want for a date.
But aggressive mamono want husbands for themselves, they're only gonna "imprison" a man if they already have one so they can get a husband for their friend/sister.
The setting may not state against it, but it's overall VERY unlikely that mamono will engage in organized slavery of potential husbands because of not only the scarcity of available single men that mamono can encounter, but also the very nature of mamono to love and desire husbands for themselves rather than trying to sell men off.
Also, mamono have "brothels" that are basicly marriage shops and not actual brothels. The employees have to be constantly replaced and they will marry their customer.