The eBook figures are based only on Traditional publisher sales and some of those include audio books!
Amazon does not publish their eBook sales. Smashwords do.
The sales of eBooks may have actually risen. However the majority are read on phones, then tablets and eink screen ereaders are third. Amazon might have 90% of eBook market and ONLY supports their app and Kindle.
An ereader is really very simple. The actual software (firmware) could have been much better than today over 10 years ago. Probably 15 years ago. The expensive and tricky part is the eink. Amazon bought and buried the Philips' eInk spin off that had produced a folding mobile phone. Almost all eink readers ever have used
https://en.wikipedia.org/wiki/E_Ink_Corporation eink. Sony had first generally available eInk reader in 2004 and it was a little grey but fine in good lighting. I tried it in shop but couldn't afford it. Amazon came late with SW based on Mobi (terrible language support) in 2007.
There is almost no HW (hardware) R&D needed, as the design is very simple and based on panel makers reference design. Most changes have been simply newer panels and cosmetic.
The SW (FW, Firmware, software) is usually based on GNU Linux or Android (Linux Kernel), a basic pair of readers (sometimes the Adobe one), one for eBooks and one for PDFs and a simple GUI. A very small R&D can build that quite quickly (and it shows).
Most of the development budget seems to be on tooling for the case, then PCB.
With a team of THREE, I built a 4G proof of concept VOIP phone with Firefox, Debian Linux, email, choice of Tile or Desktop GUI (both Trolltech Qtopia), SD card slot, USB host and slave sockets, touch LCD (eink was available, but no good for colour or video), PDF reader, HTML based eBooks, media player etc. Six months!
Forget Mirasol, it's not as nice as eInk for text and crippled by Qualcomm's royalties model even though it's colour and sort of does video
The fact is that there little incentive for dedicated ereader R&D. It's a niche. Tablets and phones are cheaper to make and commodity items. That's why the Amazon Fire is a crippled Android Tablet. Most eBooks are read on the kindle App on Phones & Tablets.
All the eBook growth is small publishers, independents and self publishing. The traditional publishers are focused on Retail who have no ability or interest in ebooks at all all (apart from maybe Barnes& Noble who are clueless).
Summary:
The Traditional Publisher figures include audio books and are not representative. They charge almost as much as for paper and almost always have DRM.
Amazon has maybe 90% of the eBook market and doesn't say how many they sell.
Indications are that Independents, small publishers and self-publishing is seeing massive growth in eBooks because they are cheaper, often DRM free and on more platforms, but not in bricks & mortar Retail.
Dedicated eReader sales may have declined because almost everyone has a smartphone and/or tablet (sales of those, esp Apple, have declined because no need to upgrade and market saturated). Over half eBooks are read on phones.
Amazon is a danger to publishers and consumers due to their market power and strategies and lack of USA consumer vs corporate protection.
https://en.wikipedia.org/wiki/List_o...ions_by_Amazon
Many makers have abandoned production of eReaders (Sony being most notable). Sony has been crippled ever since they became a media company as well as electronics (stupid DRM on Mini disc, stupid proprietary DRM memory sticks on cameras, CD root kits, DVD, Bluray DRM, reliance on ebook shop for ereader).
Current Amazon dominance and only allowing Amazon app on general purpose gadgets pretty much means anything other than Kindle is doomed. The Basic Kindle Touch has to be close to cost. I don't think anyone can retail an eInk reader at that price and make a profit. Amazon has some premium models partly for the look of it and because it's no effort to do so. Almost everyone is using the same panels.
see
https://en.wikipedia.org/wiki/Comparison_of_e-readers