Why is Volume 5 of the DVDs so hard to find?
These are available from Viz Media, in 8 volumes of 3 DVDs each.
A couple of years ago, I picked up volumes 1-3 in a pawn shop for 18 bucks each, and today I found volume 4 for $20.
After looking on a couple of price search engines, it seems that volumes 1-4 and 6-8 are available (around $32 each or so,) but volume 5 is out of print. Naturally, Amazon Marketplace sellers are taking advantage of that, I saw two copies, and the cheapest was $99!