It takes time to make sure all images and image maps have meaningful text alternatives. It takes time to perform accessibility testing and respond to the results. It takes time to program your authoring tools to prompt for accessibility. But just as the removal of physical access barriers by such means as curbcuts, ramps, and automatic door openers makes physical space easier for everyone to navigate, so it is with electronic curbcuts. As sites are made more accessible, usability is improved for all users. Among the findings of usability studies are the following facts [Donahue et al. 1999].
Each dollar spent on usability returns $10-100 in product benefit.
It can cost as much as 100 times less to fix usability problems before launching a product rather than after launch.
Usability improvements increase user productivity by an average of 25 percent, improve user morale, reduce documentation costs, reduce training costs, and reduce customer support costs.
Usability engineering has demonstrated reductions in product development cost and time of 33-50 percent.
Also, Bias and Mayhew  found that including usability as part of the design process can improve brand image, customer satisfaction, and customer retention.
If revenue and customer satisfaction are among your company's goals, you will agree that the time expended to create usable, accessible Web sites is well spent when you consider these facts; and as the population ages, the issue will become increasingly important. This prosperous, tech-savvy generation will eventually use assistive devices. Many already are. As this occurs, we may come to redefine accessibility as the ability for businesses to access this growing group of customers. In the next chapter we demonstrate this by discussing the growing number of cultural and science museums using the Internet to increase both the numbers of visitors to their facilities and the variety of services they offer via the Web.