I understand the distinction, but bands haven't turned out to be the best analogy. Thanks to P2P, etc, most bands now make little from CD sales, and have to pin their hopes on touring and merchandising - things that look a lot like "playing individual weddings and bar mitzvahs." And there was always the Grateful Dead, and Phish, The Black Crowes, etc, etc, which build a loyal following through their concerts, and encourage taping, thus in essence giving away millions of copies of their songs in order to promote their concerts and merchandise.
Likewise, for startups, the distinction isn't always that cut and dry. If you're an Oracle or a Salesforce.com (both of which were once startups) you probably had to do customization for every one of your first n clients in order to make the sale.
I think there are obviously businesses that let you scale easily, and ones that don't, and the quote above is a good starting point, but it's not a 100% clear line. And often what looks like a scalable business turns out not to be so, and vice-versa.