How much does a game have to sell to warrant a sequel?

I'm thinking about Zack & Wiki. I bought it on the weekend an my wife and I are having a great time playing it together.

There has been quite a bit of talk about Z&W's sequel and I seem to remember murmers of it being planned (don't quote me, rumors aren't reliable). Luckily it really doesn't take a lot to build a game like this in terms of investment and I'm pretty sure they've made their money back and then some on the game.

The big reason I think a sequel is likely is because the game has had a huge grassroots following to get the sales it did and the people who loved the game have driven those sales. Ideally this would mean that now that this previously unknown title is known to be good it would get a lot more coverage and potentially a lot more investment in advertising this time around which could really help sales quite a bit when combined with that grassroots PR.

Personally I think they'd be silly not to make another and capcom love's sequels so I think the odds are very good.

PS - Besides it sounds like they've already sold at least 2 copies =)

Enough to make a profit. Since different games have different development costs it varies. For example, Killzone 2 has been estimated as having a 30 million dollar production budget. At 60 dollars per copy, every copy sold beyond a half a million represents profit. If it sells more, which it most likely will given the hype, then you can count on seeing a Killzone 3.

500K I think.....

Depends on the game. There isnt any concrete number. Usually if it makes a profit that puts a smile on the developers faces, they will make a sequel.

If the developer profits significantly there should be a sequal.

If a game makes a huge profit, then its possible for a sequel

Depends on the budget. It's different for every game.

Assuming it gets back the costs it took to make the game, and makes the company a nice profit, the chances of them revisiting the game is much higher than if it failed.

For instance, selling 100k Zack and Wiki is probably a success, whereas selling 100k of a high profile title, like say Bioshock, would be an unmitigated failure.

LOL I heard Ninja Bread Man is getting a sequel (rumor) So that means there are NO standards for sequels...LOL

 the developer does not get all of the money sold on a copy of a game.  I believe the developer usually gets half of the money per copy of the game sold to retail so Killzone 2 will have to sell a million copies to break even if I am right