Average sales for indie computer games

[Charli3]

Hi,

I'm looking for an estimation of how much you can sale an indie game on computers (Windows + mac + linux) through online distribution (personnal website, steam, bigFish, ...).

I perfecly understand that the number will dramatically change from one game to another but is it closer to 1000 units ? 20000 units ? less ? more ?

I know for big indie games like World of goo or Braid. But what for the modest ones ??

Thanks

Charlie