Hey, thought I'd chime in! Those are all great ways of selling SEO.
I try to show the prospect a real pain point in their specific situation.
For example, for one local business I actually took a screenshot of a search for their brand, where they were not even showing up, and printed it and brought it to them. When they saw a search for their own business didn't even bring a result, that was motivating!
Or I'll do a really quick competitive analysis (nothing very scientific, just a real good guess at a desired keyword) and find where they don't rank well but a competitor does, and show them that.
Or, if a slightly more tech savvy prospect, I'll find a few things really wrong with the website, some 404s or crawlability issues.
If you can present these things in a way where you don't alarm people too much but generate that reaction of "wow, we need to do something about this". Present them in a way where you're also helping, educating and can provide a solution.
So my angle sometimes isn't "here's why SEO is important" it's "here's why YOU need SEO".
-Dan