Am I the last to know that Amazon can often be cheaper than eBay?

I have been keeping a book on watch for a few days, and then for some reason I decided to read the reviews about it on Amazon. THEN found that the book was routinely cheaper on Amazon that the seller was trying for on eBay and that I could actually buy the series for only slightly more than the single eBay book!

I am absolutely not going to check on books I have already bought, or I might be kicking myself!