Sealed league. Get a group of people, everyone buys 10 packs for $26, you get to open six of them and you play. Every two weeks you open another pack. Ends up taking 10 weeks and nobody spends more than $26, maybe a little more if you buy card sleeves, iPhone apps to track life, or whatever.

What makes it fun is that you're playing against people with the same size card pool as you. Draft is cheaper ($7.80) but it's over and done in a few hours.