So to back up my point lets go to the W3C Web Accessibility standards and see exactly what they list and let's see if such things are actually require such a huge cost to implement.
Text Alternatives: Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
Oh noes! An alt tag! Such a difficult thing to implement. Not only does this benefit disabled people but it also helps people who still use Lynx or other text based browsers who aren't disabled. The extra time spent on this is a few seconds at most.
1.2 Time-based Media: Provide alternatives for time-based media.
Oh noes! You might have to provide a link to a transcript of the media. While this can sometimes be a bit of a tedious process in most cases it's not as many websites have content that averages maybe a few minutes in length.
1.3 Adaptable: Create content that can be presented in different ways (for example simpler layout ) without losing information or structure.
Oh noes! Using CSS properly! Again, people should be doing it this way anyway and the only loss by having to put in this extra effort is the loss of subpar designs. Again, this doesn't just benefit disabled people.
1.4 Distinguishable: Make it easier for users to see and hear content including separating foreground from background.
Oh noes! Text should be of a color that sets it apart from the background! Oh noes the horror of not being able to put grey text on a black background! Again, this is a trivial thing to do and is also beneficial even to those of us who don't have poor vision and don't want to get eyestrain reading your shitty web page.
2.1 Keyboard Accessible: Make all functionality available from a keyboard.
Oh noes! This means using HTML controls and links! Again, another trivial thing to do.
2.2 Enough Time: Provide users enough time to read and use content.
Oh noes! One might have to put a checkbox or something else that allows people to be able to change or turn off session limits on viewing content. Again, trivial to implement.
2.3 Seizures: Do not design content in a way that is known to cause seizures.
Oh noes! One can't design web pages with annoying flashing content! I don't know of any person who would think this is a bad thing.
2.4 Navigable: Provide ways to help users navigate, find content and determine where they are.
Oh noes! Designing pages that aren't cluttered and so people can actually easy navigate and use them. This just boils down to actually designing things properly and should be a negligible cost to any decent web page designer. One doesn't have to be disabled to benefit from not having to attempt to use over-cluttered pages.
3.1 Readable: Make text content readable and understandable.
Oh noes! You actually have to make sure the content you put on your website isn't gibberish or in some sort of weird alignment or other such stupid things that dumbass website makers do because they think it's cool looking.
3.2 Predictable: Make Web pages appear and operate in predictable ways.
Oh noes! You actually have to make your website actually work in the way that makes logical sense based on the way it was designed. Oh the horror!!!!
3.3 Input Assistance: Help users avoid and correct mistakes.
Oh noes! This is as simple as doing things like highlighting fields if a user missed a required input in a form. Trivial and useful for not just disabled people.
4.1 Compatible: Maximize compatibility with current and future user agents, including assistive technologies.
Oh noes! Designing your web page to standards and avoiding using deprecated features in your web page. How horrible it would be if more people actually were properly coding their web pages.