Custom build vs theme? Are you making unique images or using stock? Are you designing any part or just setting up as is with the default theme settings? What platform are you using? What's your typical per word rate for writing content? Are you going to allow revisions?
As you can see, there are a ton of questions that you'd have to outline and answer before you can accurately quote a job. Just because someone can make a single page site for $100 from a theme and push the same content that's on 100's of other sites, doesn't mean it's worth it.
If you come back with a quote that says the 24 page site will be $5000 after all this work and the prospect says they want you to do it for $100 like Company X will do, then tell them to go to Company X. They'll come back around if they get garbage delivered and want you to fix it up.
