As a writer myself, I've paid a lot of attention to this issue over the years. Based on many discussions and observations, I'm comfortable saying that the vast majority of self-pubbed authors can only dream of sales in the hundreds. I believe most are in the dozens, if that much.
And yes, publishers are very tight-lipped about sales, but maybe some significant author will step forward in the near future and actually put a percentage number forth on e-copy vs. hard copy.
My wife is an author with 14 bestsellers in print. I am able to check her sales at any moment. I've seen the numbers of other bestselling authors she is close to, some really major authors. I'm telling you with my hand on my heart, e-book sales are about 3% of popular fiction across the board, right now, today.