I bought a 200 click solo ad from Emilis Strimaitis for $70.
Here’s my receipt:
He promoted my site Top Plugins for WordPress
I ended up getting 388 clicks (nearly double!) but a
conversion rate of just 26% (normally 37%), perhaps
his list isn’t very interested in WordPress Plugins though.
Nevertheless I added 99 subscribers to my list or basically
spent $0.71 per new subscriber which is great!