I have been writing for the web for the past 8 years and am very familiar with seo, long tail keywords etc. I can write about most subjects if you want an informational article. I can write product descriptions and sales copy. If you are looking for a creative writing service then I can do that as well.
Whatever type of writing you want I will undertake to write 400 words for $5. If you want something uploaded as a kindle book (text only) then I can edit your file for Kindle and upload to Amazon - I would expect this to need 8 gigs - so $40