Are you stuck on the idea of buying advertising on TGP's? I realize that some of them show massive traffic stats, but I've had a terrible time getting it to convert. I gave up on them, so I have no idea what their pricing is like these days.
I can offer you two alternatives. The first is Top Blogs. They have an "adults-only" category that accepts advertising in the sidebar, so it's good visibility. It's $30/month and the
Adults Only category front page gets 80,000 views/month. That works out to 37.5 cents/1000 views. I don't know if that's a good deal or not. The advantage to it is that it's mainstream traffic, people who weren't looking for porn, but were curious enough to click on the adults section. Top Blogs only lists blogs in their directory, but they take advertising from anyone in the sidebar.
The other alternative is my own
Blue Wave Links List. The best advertising deal there is a "your ad on every page" in the sidebar for $200/month. Blue Wave gets 953,000 page views/month (September's stats), so that would work out to 21 cents/1000 ad views. Again, I don't know how that compares to other places. We just started accepting paid advertising recently and chose the price pretty arbitrarily.