>> He or she is charging an absolute amount, not a percentage of their payslip.
Here's another analogy. I make this beautiful and unique item that you want to buy. I charge - literally - an arm and a leg over it. Like, the actual body parts.
You protest: "You're asking for a part of my body??". I reply "I'm asking for an arm and a leg, not a part of your body". Hey, maybe you can pay me with someone else's arm-and-a-leg, right?
That is how absurd it is to say what you just said.
>> There is no coercion here.
Yeah, there totally is. It's the same kind of coercion the Mafia employes. "You don't want to pay us to protect your establishment? Well, fine, but then something may happen to it".
You don't want to pay 70% of your income to stay at my dirty, dilapidated hovel? That's fine, but then you might find yourself homeless.
The tactics are similar because the mindset is similar. Pay up or else. It's exactly how it works and it's precisely why it's coercive and morally repugnant.
More to the point: I find it morally repugnant because I don't have to pay 70% of my income to stay at a trailer, and I make probably 70 times more than the people who are forced to live there. There is no excuse for that. If I payed 70% of my income to live in a shithole, then I would think, OK, that's how it goes. That's life, see?
Except, it's not. I know it's quite easy to get a much better deal, as I got. If someone forced me to live in such conditions, I'd be up in arms. Therefore, I also do mind a lot that other people are living in such conditions.