I don't know if any of you have seen this, but Wal-Mart has loads of Value Packs with waves 5, 6, and 7 in them. I ended up getting all of waves 6 and 7, except that funny Gun Station with Big Brawler. I recommend buying the Wide Scope/ BAT 3.2 pack. The SWAT dude is awesome. There's also Value packs of some vehicles with wave 2 of the Mision Discs, and the MDs can be bought on their own for $4.
I also found wave 8 at Target. I ddin't find Zarana, but I did get Cobra Commander, who's all sorts of cool now that he's got the faceplated helmet again. Heavy Water, the new Cobra waterman, makes me wish Hasbro came up with an Eels redux.
I think I've spent about $45 on Joe stuff this week alone.
But it's fun.