You own a store (hypothetically) selling let's say, balloons. Your profits are low because, well you sell balloons Approaches an individual with a pocket of cash prepared to purchase a lifetime supply of balloons and. . . . he enters the balloon store down the street. Why? Because the individual is in a wheelchair and your store is not wheelchair accessible.
We're taught the customer comes first but the customer can't even get through the door?! Now imagine this problem, but multiply the possible shoppers by twenty and each can easily jump to the alternative (accessible) store in seconds. That is what it's like with a non-accessible website. Oh yes, these websites do not only cause trouble for disabled online shoppers of which there are thousands, but it hurts your bottom line as well.
Beginning with our original analogy lost transactions. If it because frustrating or difficult to navigate a site, read product reviews, complete forms chances are you'll lose the customer to a website which made the extra precautions.
Your SEO score could be impacted. For those of you who don't know what I mean by SEO score; it's a measurement of your websites popularity amongst Googles search algorithms. The higher your score, the higher you place in googles search results. Affecting this score are items such as Alt descriptions, sitemaps and header tags all essential tools used in creating an AODA compliant site.
Word spreads, people talk, if it's discovered your website is too difficult to use, others who share this dilemma will likely be given the heads up. Not you haven't just lost conversions you've lost web traffic altogether.