Here are the results* from a 100-click solo ad I bought from Liviu Ungureanu. You can find more reviews in my solo ad directory.
Clicks bought: 100
Clicks received: 138
Optin percentage: 42%
% Tier 1: 71%
Cost Per Optin: $.52
You can buy a solo ad from Liviu at his website.
*These are the results from my squeeze page and sales funnel. Your results may vary from mine.