Lame: $100 Adequate: $200 Good: $500 Famous: $1000
Overview: http://www.headshots101.com/head-shot-price-ranges.html
Examples - get a sense in advance of how you want to present yourself: http://studiomark.com/headshots.html
Prices above represent 1-2 hours of work in the Bay Area. I've done a lot of business with still photographers for film projects, so they're pretty current. The camera is just the recorder. The 'look' requires 3 lights, some assistance from a makeup artist/stylist, and a sense of what you are trying to project as well as what makes you distinctive and which parts you want to emphasize, or not. If you don't have great taste in clothes, bribe a lady friend who does to take you shopping. What you like/dislike about the way you look/dress is not necessarily what appeals to others.
Have a few similarly themed choices - if you are a suit-and-tie guy, then you want a few different combinations, plus a few shots of just shirt and tie, or sleeves rolled up (for those 'straight talk with jdavid' articles) and one with your collar loosened 'jdavid's 2 cents'). Also you want a mix of closeup (head & shoulders) and medium (waist up) shots to give to magazines and blogs. Eventually one characteristic shot may become the best known, but it might not be the one you expect - have several and rotate them to find out what your readers like. Don't limit yourself to one great shot, or you'll seem one-dimensional. And don't put your picture on your business card unless you want to be remembered as a realtor and insurance salesman.
I can refer you to a friend of mine who's quite good and would probably charge you $400, but he makes his business mainly in family pictures with a little fashion on the side, so you may or may not like his taste.