I don't offer SEO service myself but I think I would charge on how difficult to rank the keywords and their profitability. For me as a client, I would have no problem paying $5,000 monthly to rank keywords that make me $100,000+ a month, for example.
I am sure if you can make your client see the benefits and money he'll get using your service, I don't think it'll be hard to close a deal with him. But be careful with the promises though, because most people don't understand SEO and they expect too big or too fast results.
I am sure if you can make your client see the benefits and money he'll get using your service, I don't think it'll be hard to close a deal with him. But be careful with the promises though, because most people don't understand SEO and they expect too big or too fast results.