UK Agency Pricing?
I'm sure there are others, but spotted this on Amazon.co.uk this morning. It came up in my recommendations and I went to have a look as I'm pretty sure it was £6 - £7 last week.
It now says 'this price was set by the publisher'.
I haven't seen any more large price hikes so far - and this book is supposed to be an 'enhanced' version - but looking at some others, even if the price has not changed significantly, the 'price set by publisher' line is appearing on several.