Bastion (Book 5 of the Collegium series) by Mercedes Lackey (all prices US$):
ebook (Amazon, BN, Kobo, Google Play Books, Books A Million): $12.99
mass market paperback (Amazon, BN, BAM): $7.99
(I just re-checked the prices a few minutes ago.)
For over a year. Book 6 is out now (also $12.99 - but it's still in it's "New release" year....)
$5 more for an e-book? NO. Just....NO.
Don't know if it's the publisher (DAW/Penguin) or the author - but it is consistent and ridiculous.
Further reading of the Valdemar group has come to a screeching halt, for me. And, since I like to re-read the whole group....well. None of them are getting attention while I remain annoyed.
Meanwhile - has anyone noticed that C. J. Cherryh's backlist is just quietly appearing? I keep looking (waiting for the next Foreigner cover to show so I can pre-order it). The Morgaine omnibus came out in pb and ebook recently (with a preorder stage), but now other "holes" in her backlist are just showing up as ebooks. Not sure on the exact release dates, but I noticed (and promptly bought) Faded Sun omnibus 10/7, and Chanur's Homecoming 10/16. At "normal" e-book prices (parity with MMPB's). Finished Faded Sun on 10/8. I can finally start a re-read of the Chanur series - now complete in e-book format!