Cost can very based on the professionals experience. You could always contact a photography student... they can probably do a great job for little expense.
I had a buyer walk into an open house and ask me who the photographer was who took the pics . . . . as they had seen the house before from realtor emails and had never envisioned it as they had when I took the listing. Not trying to toot my horn here, but to emphasize the difference good pics can make. Every survery you read or buyer u interview will tell you how much they rely on the pics.
Rather than spending oodles of money hiring a photographer, I would suggest getting a basic photography book to learn what catches people eyes and what doesn't. (with my focus on my business degree, honestly, my photograpy isn't that great . . .but the basics do help)
However, I do agree with Ian that video seems to be the upcoming trend. Many websites such as Realtor.com are now including it as an option. I'm thinking it is going to replace or one up virtual tours. Ugggh, I have to learn something new . . . . guess so!