Hi Robert, that is a really interesting selling point for SEO as a practice. I think it is quite surprising the number of individuals who won't sell SEO services because it feels cheap. My feeling is that this is a business like any other and provided we are offering a high-quality service, educating clients and managing their expectations SEO should be sold.

Here are some of the major selling points that we use when pitching to clients...

• Getting your products and services in front of prospective customers at the moment they are actively looking for (or at least thinking about looking for) whatever it is you offer
• SEO is subtle and doesn't interrupt - you're not stopping them from doing something like a TV, radio or print ad does, you are assisting them in their problem solving quest. (related to the first point but this one is a clear comparison of SEO vs other marketing methods).
• Build trust and credibility in your industry - this point can certainly be debated but we remind clients that with other forms of marketing you are simply buying attention whereas with SEO (and the peripheral activities) you are earning and building trust. Ranking #1 organically for an important term can be beneficial to your business beyond the traffic it provides.

Hope that helped - I'm interested to hear others thoughts also.