WCAG 2.0 Accessibility compliance is within reach of anyone following the most basic of best practices in web development these days.
There are many powerful free tools for developers to use to test and validate their work as they go, and there is a ton of literature and thought leadership out there for anyone to find and learn from.
OP may be referring to retroactively making websites accessible, since it can be a lot of work to fix something that wasn't built with accessibility in mind from the start.
Just like adding a sunroof option to a new car is much cheaper than adding a sunroof to a car that didn't come with one in the first place. ;-)