Can you tell me where I can find the best ghostwriters?

[CyberAlchemist]

Hi everyone,

I am looking for high quality ghostwriters to write a short ebook outside the marketing niche.

I have found a lot of websites for that:

Elance
Fiver
Odesk
Freelancer
Webmaster Sun
Writerlance
etc...

Can you tell me from your experiences where you could find the best quality writers ?
What is the average price for a 15 page ebook ?

Thanks in advance.
CBC