Is this a serious question?
Why do people think sales should be directly proportional to downloads?
Sales depend on
1) what you post
2) how you post
3) where you post
4) luck
5) filehost
Finally someone smart to say that !

Number of downloads is stereotype , carrot on a stick and nothing more ....
You can post on several main forums and expected sales , or post on another 1000 forums with minimum 1000 DL more , but you will see ( reported ) sales only from several main forums .
Many time I asked myself where are sales from this other forums ? People don`t buy premium there ? Or the file hosts take this sales only for them - they can do this , because these forums are irrelevant for them .
Posting only on a main forums you can`t have a lot DL , maybe only with spamming ...