Should authors offer Kindle books for $.99 to get maximum exposure, or is that just undervaluing our work?

[Boyd]

All of my Kindle books are on sale for $.99, including my new novel, my three memoirs and my two volumes of short stories. I decided to do this in recognition that I am not trying to make a living from writing. I am retired. My interest is in getting my writing and ideas "out there" to as many people as possible, and lowering the price to less than a dollar seems to be the way to do that. Please check out my books here.
http://www.amazon.com/s/ref=nb_sb_nos...

I'm sure you know that even if you don't have a Kindle reader, you can download Kindle software for free for any device you have here.
http://www.amazon.com/gp/feature.html...

[Mellie]

If you have everything available for free or only 99 cents how do you do any promotional work? Most sites require price to be discounted for you to advertise.