If you have a Goodreads 'To-Read' list and would like emails when the ebooks' prices change, signup for a (free) account at Luzme.
Same for Amazon wishlists too...
Countries: USA, UK, Canada, Australia, India
Stores: Amazon, Apple, BN, Kobo, Google, Sony, Smashwords, etc.
Give it a go, you might save some money on your next ebook