There is also the case for a potential increase in his conversion rates as a result of adding SSL. Online shoppers I've observed in usability sessions often sc

There is also the case for a potential increase in his conversion rates as a result of adding SSL. Online shoppers I've observed in usability sessions often scour sites looking for evidence of security measures (e.g., green EV certs in the browser, various icons in the footer). This is especially true when you're asking for something like SSN info... If appealing to the desire for security of user info doesn't work (unfortunately), appeal to his desire for more customers...