I had the same problem months ago when I wanted to get the Azumanga Series. I was torn over the fact that the 6 volumes cost $20 each. But then right before ordering the first one I found they sold the entire series box-set for only $50 on this one site, so I got it.
Kindle Reading List (163,457 Locations Completed)
Finished: Aquariums of Pyongyang (2535), Under the Loving Care of the Fatherly Leader (24,074), The Lone Samurai (4753), Nothing to Envy (5349), Shogun (26,263), Eating with the Enemy (9170), Fight Club (3218), River Town (7524), Don Quixote (21,430), The Party(6492), Bravo Two Zero (7340), Rogue Warrior (7602), Mao's Great Famine (11,059), His Dark Materials Omnibus (20,766), Moon Lander (5882)
King Rat (9308)