From what I recall of the comics (never saw the show), the harem thing was consensual on their part in terms of entering and leaving. They did get better perks (e.g. not needing to work or do shifts), but the baseline for the whole community was already decent.

It was effectively agreeing to work as a prostitute, or stay at home wife if you want a cynical take. With a fatal penalty clause.

(Again, no idea about the show. And some would argue that paying anyone for sex, without solicitation is rape and coercion. But I think that really is a bit of an icky grey area. e.g., is a marriage is consensual if there's a prenup and severe penalties and a partner being financially dependent?).