[casual_games] "Typical" sales figures for a casual game?

[Greg Maletic]

Here's a really broad question that I know is hard to answer: what  
are the "average" download and sell-through numbers for a typical,  
run-of-the-mill casual game assuming it's distributed through major  
online portals?

I know, I know, it's a tough question. There are a thousand variables  
involved. But there must be some ballpark numbers that people in the  
industry toss around when discussing the market potential of a new  
game. (If "average" is too challenging a term, here's another way of  
looking at it: how many downloads/sell-throughs does a game need in  
order to be considered a "hit?")

Any help would be appreciated!

Thanks.