I think you're wrong about assholes. Assholes can easily form long-term social contracts, though such contracts are often abusive.
I think the people the OP is referring to are simply socially inept (as you also noted). They may have an illness (such as Asperger's) that renders them unable to form strong social bonds with most people. And so they are lacking a very significant part of life. Paying for social interaction is a way for them to fill that necessity. The problem is that they become chained to that, as they're not getting it anywhere else. Obviously this leads to difficulties as SPs are often highly desirable and therefore have their social needs met elsewhere, and so they don't form the same bond with their clients. No relationship is more toxic than where one party is absolutely dependent and the other party is independent. Obviously such an arrangement leads to a dissonance of respect, and feelings of ill will on both sides. Over time the relationship breaks down and gets increasingly nasty.
I don't know the OP in this case, but how innocent is she in this situation? She admits that money was a factor and she didn't want to lose what I'd call "whales", and so continued her relationship with them despite knowing things were off. What worries me the most is that she says she tries to maintain "friendships" with all of them, which tells me she is absolutely crossing the line between business and personal.
As with most situations, both parties probably bear some responsibility, and as is often the case, neither party will admit their own.
