That's the EXPECTED RESULT of ending a year's long suppression of prices by a monopolist, in this case Amazon keeping Best Sellers and A-list eBook at an artificially low price to keep any potential competitor out of the eBook market by selling the at at least $5 per book below what they paid for them! It is perfectly normal for a suppressed price to find a new normal price when the anchors are removed from the normal market pressures.
Thank you for admitting that the Apple conspiracy worked to raise ebook prices.