As an
SEO firm, we've been fooled more than once by HTML extensions only to find that a site was done completely in PHP and draws from a database.
If you want an accurate quote, the person needs to see what they're going to have to work with. A database driven site may need much more work than one would think to create dynamically generated title tags and meta tags.
With that said, they should be able to give you a "ball park" quote based on whether the site is considered to be static HTML or drawing from a database and they should be able to reserve the right to turn down the job if they are hit with a surprise and a database that they can't work with or get access to.
Source code, as stated earlier, only shows the completed HTML code after the browser compiles it. The
SEO firm needs to work on the raw coding.