So as I was chilling in the hot tub at the at the Florida show and a prospective customer pointed out that the Profitability Calculator we have up at
CJTraffic.com - Available Now Page was useful, but didn't help for webmasters that offer trials.
So, to get that incorporated I had to build an excel sheet that could handle this and then have my designer port it over to hahahahahahahahahaha. It'll be up on our site by the end of the day.
BUT, I realized this excel sheet could be useful to anyone who's buying traffic from anyone else. All you need to do is change the clicks and price fields to whatever source you're getting the traffic from. Then just like on ours, input your conversion rate, monthly rate, retention rate (and now trial cost and % conversion to full join) and it'll quickly give you an idea of the profit to expect from a traffic buy. So feel free to download and tweak. Hopefully this'll help people make more intelligent traffic buys:
Download CJTraffic.com Profitability Calcultor
Enjoy!