For most, sales stay the same, regardless of how many items you have. Many even report less sales with more items, which is simply the effect of what I said above, most tracks have a rather short lifespan before they disappear forever.
It’s key to remember that for most authors sales are NOT correlated with the number of items. Again, you might win the lottery and by all means stay positive, but don’t order that Ferrari just yet 
Also see this thread for an ongoing discussion and cospiracy theories AudioJungle Sales Monitor