My view on prices has always been that it's all down to supply and demand.
A lady should just charge what clients are prepared to pay. She will know this from how busy she is.
If she's knocking back clients then she should put up her prices.
If she is short of work, then drop them a bit.
Also remember location location. The same lady might not be able to make a living charging $200 ph in one location but in another, $600ph might keep her busy. Where I live there's no w/l's at all - not even privates. One lady on tour here recently was charging $650 and doing really well apparently.
So if I was a w/l I'd be charging based on the demand. I'd love it if ladies charged what I could afford, but in reality they are in business first, so like any business, they should charge what customers are prepared to pay. This is why I find if I am prepared to travel anywhere, I can find a great lady who is working in an area and can only charge maybe $150 or $200 p/h. The same lady with the right marketing could relocate to my town and charge a lot more.
Questioning a ladies rates doesn't make sense based on what I've said, because if she's charging $$$ per hour and it's working for her, then a client complaining saying she's not worth it is just insulting. Her value as a service provider comes down to if she's making enough to satisfy her financial requirements and are clients prepared to pay her hourly rate? Well that's the business angle. Mind you, personally I'm crazy so if she's a sweetie I'll pay whatever just to talk and cuddle her... shhh wait! did I just say that??