Expensive virtual assistants

In DigitalPoint forums, I saw some threads which they offer their services as virtual assistants. Virtual assistants are the ones who can maintain your site, forum or blog's traffic and popularity. This is another unique SEO position I've ever seen. They will cost you in a monthly basis only, just to keep your site on it's proper ranking place. There are many expensive virtual assistants at DigitalPoint, and they are ranged from $200 to $400 monthly for their lots of services like Angela and Paul's method, link building, advertising, promotion and so much more. In the Philippines, I know one virtual assistant who can do the same services for only $75 monthly. But why is that it needs to be expensive? Is it because of their expanded services? I think so, but to make sure that they always send reports to you through e-mail.