Hiya! I used the Freebooksy series promotion ($150) in August 2020 for my sci fi/contemporary fantasy dragon hunting series. I had 1104 downloads, 41 sales, and 25 pre-orders of the newest book in that series the day of the promo. I was also very fortunate to get an increase in Amazon ratings on the first permafree title, Of Cinder and Bone, since then. I'd say I've gotten around 10-20 new ratings since that promo ran. I made back almost the entire cost of the promo on the first day and I think I made the entire cost back in a week. Overall, I felt pretty satisfied with the results, but it's definitely something I'd only do about once a year given that high price tag. I had been hoping for closer to 2,000+ downloads, but it has been a bit of a tough year and I'm also a nobody. Hope this helps!