I'm very picky about my cases. I want something strong, yet is not too bulky on the shelf. Multi-disc Alpha cases waste space. Those cheapo cases from places like Meritline are flimsy.
This is what I like:
Single sized double (Memorex)
Single sized triple:
Single sized quad:
1" spine 5-disc (Nexpak)
1" spine 6-disc (Nexpak)
1" spine 7-disc (Nexpak, Alpha)
Use a 1" six-disc and one of these add-a-pages:
1" spine 8-disc
1" spine 9-disc
They have these, but I never use them.
I use 3 triples instead.
1" spine 10-disc
I use doubles, triples, quads, and 6-disc most often.
Though prices have come down a bit this year, most good cases still hover around $2-4 each after shipping and transit loss (tossing ones broken during shipping, always order more than you need). This is how I store a great many of my DVDs. The rest of my collection is on spindles, temporarily at least.