daniel c. great question - we should have more resources around this!
For starters, you could look at using the sitemap tool to price projects with this doc: https://www.relume.io/resources/docs/using-the-relume-site-builder-for-pricing-projects
As for selling websites, you could effectively import an existing website using a URL, generate a style guide concept and send that to a potential lead. I would highlight the differences and why the client should care about them. Focus on their end customer - not on the client. How will the customer benefit from having a better website. One clear way is if their current website lacks on mobile and then throwing them a stat about how many users are visiting a typical website via mobile device.
I'm sure there are other strategies on Youtube or even on our own socials - instagram.com/relume.io
