Come on man. Respect yourself, and respect the industry. Once you sell some pictures for a far, far lower price than they're worth, potential buyers will only offer you lowball prices. Not only are you screwing yourself over, any company you sell photos to for far too cheap will expect the same low prices from all photographers, so you're fucking the whole industry right in the ass.
If you are really serious about becoming a pro photog and selling lots of work, to magazines, advertising companies, and the like, you should pony up and buy fotoquote. It's the standard for pricing among pretty much all the pro photographers out there.
http://www.cradocfotosoftware.com/fotoQuote-Pro/index.html
If you're too cheap for that, don't think you'll be selling all THAT many photos, or just don't want to, use this stock photo price calculator.
http://www.cradocfotosoftware.com/fotoQuote-Pro/index.html
It offers a better solution to figuring out prices than just making them up.
One other thing you should keep in mind, is that it is always better to price too high and then let them fight it down than it is to propose a price too low and try to barter it up.