You also need to factor in copyright on the images, a cheaper photographer may well retain copyright and will not provide you with the original high resolution images, you'll then have to order all prints through them, probably at a high premium per image.
We're now at the point of looking for a photographer for our wedding, fortunately I know of a truly excellent photographer who've I met previously at a party and I've seen plenty of his work. Not cheap, not expensive and we retain the copyright on the images, he always supplies his clients with the hires images.