Human costs are variable. As an aside, let me point out that you can't find any substantial computer company, software, or web site, that doesn't have a usability group. There's been a total wave of change primarily because of the web. It has played a huge role in the shaping of the usability field. Web companies, for example, recognize that the web is a continuous purchase decision.
Every click is a purchase decision.
Also, unlike software, the costs of poor usability are immediately evident. With software, the company has your money, then you experience problems. You buy the software, take it home, and then the problems hit you. With the web, the web site must prove itself to the user, or the user will leave before the purchase has been made. Usability is immediately important and cannot be ignored on the web.