Over the years I always find and buy the best quality diapers at the lowest cost. My secret is Nextag's Radar system. You get to set the price you want to pay and when the diapers go on sale you will receive an e-mail. You request what you want and it goes on the radar screen until the price matches your request. You also get to compare with several other suppliers.
I recently purchased a case of Tranquility ATN Medium (96 diapers) for $67.00 which included shipping. The cost per diaper was around 69 cents. It is the lowest price because you set the price on the diapers you are looking for. The site is Nextag.com