How much does a temp agency pay a company? How much should I request if I go permanent?

I just started at a good marketing company through a temp agency. Through the temp agency I get paid about $14 an hour...how much do you think the temp agency makes with my employment? If I go permanent, I would like to get at leat $18 an hour plus benefits...is this reasonable? Please help.

Sorry, i meant, how much does a company pay a temp agency? But anyways, thank you for your answers... I would like to hear few more responses. Does anyone have experience with temp to permanent hire? I consider myself skilled with a bachelor's degree also seeking to get my MBA part-time in the Fall of this year...so I just wanted to know if my offer of 29% raise (from $14 to $18/hr) is reasonable, especially if a temp agency is making about $10 or more for every hour that I work. Thank you for your help.

The company does pay the agency and not the other way around. You have to understand that the agency has to also pay some things that the company normally pays. They have to cover all of the taxes, unemployment taxes, workers' compensation insurance, liability insurance, and fiduciary liability insurance. So those costs are built in.
I would worry more about doing your job in such a way to show the company what you are worth. You would have to be worth a lot to get a 29% increase in pay after 6 weeks. Maybe you are that good but normally a company would only pay you what you are making at a temp agency or the normal starting wage in the company based on your position and skills. Most companies take that into consideration at the time that they hire the temporary agency.

It depends on what they negociated. I could be anywhere from 10 to 50%.

Don't worry about that. It is not relevant. Ask for what you are worth to the company.

BTW: The temp agency does not pay the company, the company pays the agency.