I did a small test for one of my mainstream projects this week...
15k Popunder (Geo filtered to US/English visitors only, Excluded mobile traffic)
Results...
Made 1 $43.00 sale so I came out (-$1.25)
I'm okay with this as the one sale may come back and purchase again in the future as I did use tracking code in the link and even if I don't see any additional sales in the next few days or week or two I basically just bought 15k unique eyeballs for $1.25 which is worth it for branding purposes
Test #2 another 15k currently running, Test #2 was modified after spending some time in Analytics and filtering out all the bad traffic sources from Test #1