Not all books are less expensive at Amazon... Some prices are fixed by the publisher and all stores are prevented from discounting. For example, The Drop by Michael Connelly is the same price (14.99) at Amazon, Kobo, BooksOnBoard, Diesel-ebooks. No discounts permitted by the publisher. However, if you were purchasing a book without this restriction and you were to use a Kobo Discount Code which is generally always available and posted in this thread,
https://www.mobileread.com/forums/sho...+discount+code
you could save 20-25% most of the time and on
many books. It always pays to check as I have regularly found that books are cheaper on Kobo as they often offer books at a "discounted" price and then with a coupon code applied on top of that, the price IS lower than Amazon even taking into account that taxes are charged.
US booksellers do not charge Canadian tax on ebook purchases. Amazon is not unique. Books bought from BooksOnBoard or Diesel-eBooks for example, also do not have any tax charged. Kobo does not have that option...being located in Canada it is obliged to charge Canadian taxes to its' Canadian customers.
To make comparing prices easier, Calibre has a feature that allows checking multiple sources (bookstores) for the price of a specific book by clicking on the Get Books icon in the toolbar.
Also, there are ways of getting US books and pricing such as buying a gift certificate with your account on BoB or Diesel, opening a "US" account on the site and then using the certificate to pay rather than a credit card.
There are many ways to obtain the cheapest price. It pays to shop around...