One of the reasons Amazon has such an overwhelming hold on the e-book market, is that it is the publishing platform of choice. It's easy as pie, keeps good records, and pays regularly on time. It's all good from the authors point of view, really.
However: IF a book is published via KDP, you may not price it lower anywhere else. No sale at Kobo, or set it free on Bokia in Sweden to get some leverage in a new market, you'll either get a letter from Amazon demanding you change the price, or they'll price match your book and make it free in the main .com store too. At least, in the US that's true, and it was for the rest of the world until quite recently (August 2013, in fact).
Is it coincidence that since last summer when indies were allowed to list cheaper on rival sites in the EU without Amazon interfering, Kindle Germany’s market share plummeted, from around 90% at the end of 2012 to (estimates vary) between 50%-65% by the end of 2013?
http://ebookbargainsuk.wordpress.com/2014/02/13/a-reminder-that-amazons-pernicous-price-parity-claues-is-illegal-in-the-uk-and-eu/ has a quite thorough run down, but that's an astonishing drop in market share in a very short time. Clearly people *will* happily purchase elsewhere, if given the chance.
To add a few points not mentioned in that article: Samsung has monster market share (40% in the big five markets in the EU) on the mobile devices market, and recently removed their own book store and replaced it with Kobo. That's kobo pre-installed on every Samsung device out there (that's three in our household of two people, alone). Google Play Books is also pre-installed on pretty much every android device around. Again, huge market share, 70% of the market in the EU. Four of those in our house. Unlike in the US, most phones here, even if telco locked, run the stock operating system provided by the device manufacturer rather than some customised "AT&T version", and actually it's several years since anyone I know even bought a telco locked smartphone. So when I say every Samsung device I'm being literal.
(Market share info from here: http://techcrunch.com/2014/01/26/kantar-android-sales-in-q4-grew-in-all-big-markets-but-leader-samsung-now-under-real-pressure/ )