Also: the very first tier should be $5 and get the donor's name in the credit scrawl.
Ptarth: I don't think he meant for that tier to include the game. It's literally just paying to get your name in the credits and nothing else.
Backers could be granted access to 'what content should I implement next' polls, possibly with higher tiers getting more weight in the polls. A slippery slope, but if there's a particular unit or minor faction you really like, maybe people would be willing to pay extra to see it available upon release.
Or, you can sell vetos! +$20 to guarantee your least favor unit (*cough wrath lances cough*) never returns!
On pricing: I've paid, I think, $16 for AI War; $4 for the bundle when i first got it, $4 for Destroyer of Worlds, and two $4 bundles to try to get friends into it. I've paid $25 for Endless Space total (including the expac). I've played 50% more AI War than Endless Space; I have almost nothing left to do in Endless Space that interests me, and I've barely scratched the surface of AI War. I think you guys are releasing expansions faster than I can finish campaigns based on those expansions (I love this game but FARK am I slow at it), and those campaigns are only getting maybe half the content from those expacs. I have a loooot of AI War left to play. AI War is a ludicrously, insanely cheap game for the hours of fun I've gotten out of it.
I've seen tons of games sell the soundtrack separately or as a premium bundle.
Wallpapers, or other downloable goodies?
Challenge Scenarios! Okay, so I don't know if this makes any sense really, but there's the various Lobby setup scripts, right? What if, rather than just having your name in the credits, you had your name in the lobby as a setup script? I dunno what a Kahuna scenario would look like, but I'd guess it involves Raid Engines and Black Hole Machines and pain. I think this would be a great way to honor some of the great AARs that have been posted on the forums, as well; thinking of the epic RockyBst cage match and Ride the Lightning. Take the essential elements and condense them into a script. This might also help people explore the different ways people play AI War, which is always good. It should avoid some of the usual problems with backer-contributed content, as well, since they'll be building out of existing components rather than having to try to implement their vision for a unit, or whatever.