it all depends on a few things... how cheap the company is, how fast the pace of business is, how reliant the company is on IT, and of course your own skillset and experience level.
the first being easy to figure out, most companys these days will try to nickel and dime you down to minimum wage. the second, is more or less the stress factor. Third, if a company only uses computers to send email and browse the web, chances are they wont pay you too much. but now say the company has 20 servers and if one of them goes down, business productivity slows by 15%, then they would probaly pay more... this ties closely in with my last point - your own skillset. if youre an admin thats slick enough to keep all your systems going, integrate tech according to business models, maintain a secure/redundant infrastructure, blah blah blah, then you probaly have valuable skills and lots of experience... that stuff doesnt come cheap.
in your case, i think the salary varies alot. im sure you can google lots of salary reviews or check out some of the salary calculating sites like salarywizard.com.
when i worked as an IT doing support and website stuff i started off at $15 an hour and was making close to 20 before I quit. This was around 4 years ago.