This is rather tough to give a considered answer. All of these add various amounts of labor to the end product, which should be translated into price.
If it helps, if I were to break down the time and effort into percentages:
93% of time spent (work) I've done is the core product. This includes the writing, layout, corrections from editors, etc.
1% of time is spent creating a printer-friendly version
2% of the time is spent on creating the RTF version
1% of the time is spent running images through a batch process to make them printer-friendly
3% of the time is spent creating tokens and mark down files.
So to be honest, those things are just a minor increase in work. The vast majority is the initial writing. The rest is just basically cutting and pasting into different formats. Honestly, I'm not sure why more publishers don't do this as standard.
*edit: I have done a readability version before, and that took me over a week, because I had to redo all of the formatting and layout from scratch. Still, that's only a week or so worth of work, compared to months of writing it to begin with.
TLDR version: it takes 6 months to write and layout the core PDF/book, and only an extra 2 weeks or so to create all of the above extras.