What is the actual cost of a full-time employee? 
Assume a minimum of $25 per hour at 40 hours per week. Over the course of a year you're spending $48,000 on salary alone. Add in the cost of health insurance, taxes, 401K, etc. at approximately 30-40% of salary and you're spending about $64,800 annually for your full time, in-house employee.

Don't forget the less obvious, and difficult to quantify, expenses such as overhead related to time and money spent filling and training your position, the cost of computers and other office technology, office space, lunch hours, sick and vacation pay, and numerous wasted, non-productive hours on the clock.

Compare to the cost of working with a Virtual Assistant:
With a Virtual Assistant you don't pay for lunch hours, sick leave, or vacation pay; and there's no such thing as paid down time because a Virtual Assistant invoices only for the exact time spent and materials working on your projects. There's no need to supply a Virtual Assistant with a computer or other expensive office equipment because a professional Virtual Assistant operates a fully functional home office. And, as an independent contractor, a VA handles their own taxes and benefits.  With a VA, you're cutting overhead and increasing productivity because a My Right Hand Girl works for you only when you require it.