It depends from vendor to vendor, imagine buying 50$ in FB ads, does that guarantee any sales? Solos are no different :) Its just advertisement, not a guaranteed money machine.
If someone did they would be found out quickly with all the udimi tracking and filters. There are so many variables that go into someone buying or not. Are you trying to go for a quick sale or building your list with a special bonus offer for your subscribers?
I ordered solo ads twice and had some opt ins but I do not have access to program's autoresponder. Then I checked the emails at backoffice and found out some of them do not exit. Fake email addresses. My mistake on that part. So now I have my own autoresponder so future opt ins have to click their email addresses to get more info so that way I will know that their email addresses do exit. Will try solo ad when I have enough funds.
Stick with top sellers. Check their reviews and comments from other buyers. Test with small qunatities fisrt
I have 2 orders and got some opt ins but no sales. Do sellers use PTC? No offense but something is not right..