My first thought (after the obvious "wow, talk about indelicate handling of a topic!") is that this presumes that all sex work occurs in the same context, and that's...not particularly true.
We've only very very limitedly had any discussion of stuff relating to sex work in my DW game,* but I can say without reservation that sex work occurs in the setting. It's almost certainly disapproved-of for many of the same reasons it was IRL (the risks associated with it, for example), but there may be fantastical considerations in play. For example, perhaps some species are not interfertile with one another, but are anatomically compatible. This would address both the concerns about illegitimate children, and potentially concerns about STDs if the two species are different enough that they can't typically pass on infections.
The price of the work would, almost certainly, be heavily influenced by location, social class, time of day, whether the workers have organized, etc. I don't think the dominant religion (the Safiqi priesthood) would practice "sacred prostitution" or anything of that ilk (whether or not such a thing was real IRL), as I've characterized them as being pretty restrained in a variety of ways. Most of their temples don't even have much in the way of decoration, because they are concerned that worldly goods (such as golden filigree etc.) would get in the way of devotion and moral rectitude. They do sponsor art galleries, though, so perhaps there's an aspect of the One associated with sexual pleasure? Could be an interesting thing to talk about, should my players be interested. I doubt I'd ever broach the subject myself unless we were already talking about it.
*Technically, we know that BDSM-related houses of negotiable affection exist, but other than knowing that they exist and that a particular briefly-relevant NPC visited one, the subject hasn't come up.
