After helping a fair number of sites I can tell you that it is not possible to fairly price
SEO for a site based on the number of pages. It has much more to do with the competitiveness of the keywords that are appropriate for the site, sometimes with the site itself, and most often the expectations of the site owner.
Casio and Porn sites might snap up offers of good rankings based on an
SEO price of $1000 per page, and mom 'n pop shops might often see $1000 for the optimization of their entire site as too much and yet both could be right.
But despite all the bad press (or sour grapes or whatever)
SEO pricing, like everything else, is dictated by the market. If there is not a decent return on investment for the money spent on
SEO, then that
SEO will not be in business long.
That said, there are SEOs who will not look at a job worth less than $10,000 and there are others who claim that they will get you top rankings for $39.95.
For the customer to choose wisely can be difficult and time spent on forums such as this will be worthwhile IMO.
For the
SEO its much easier to know if his prices are fair. When customers come back to you and tell you was money well spent, then you know that your pricing is fair.