"My point is that the percentages of disabled users are often far below what would make financial sense to support"

Yet every dollar spent focused on web accessibility further improves the usability of the site for your entire audience too.

I rebuilt the Legal & General's online home insurance purchase flow. That resulted in a doubling of the number of people completing an online purchase.

http://www.w3.org/WAI/bcase/legal-and-general-case-study

There's a before/after graph in my presentation: http://isolani.co.uk/presentations/wsg/