That was me, I think.
I don't think he's punishing Alison for anything relating to prostitution. I think he's just selfish and doesn't give a fuck.
He said he was a serial cheater before meeting Alison, which means that he consciously made the decision to betray someone else's trust not once, but repeatedly. Then, when he came here to talk about his relationships and his experience with polyamory, it was all about his happiness. It wasn't about what was good or healthy for Alison or Fran. (I was surprised by that, because most polyamory types play up how emotionally and psychologically healthy the lifestyle is.)
Unlike a lot of people, I don't think the polyamory was Alison's idea. Jake is the one who's invested in it. He's the "reformed" serial cheater. He's the polyamory life coach. He's the one with the steady side piece. He's the one who runs polyamory meetups, and if he's running those meetups, it's a safe bet he has more than a side piece.
Meanwhile, there's surprisingly little to suggest that Alison is interested in polyamory.
People seem to have created this narrative in which Jake was a naïve beta doofus before being seduced by Alison and her perversions.
However, I think he's more like the repressed loser in high school who later discovered that he's pretty good looking and can get a lot of pussy. I think he sees polyamory as a way to get a lot of pussy in a more or less socially acceptable way, at least in Millennial Seattle geek circles.