Free duh..
I think $29.95 is the perfect price for a membership given you have an attractive tour and nice join page. You either have super intriguing content or you don't. If they're gonna sign-up they will, IMO, it doesn't matter whether it's $20 or $30.
Very few people "shop" for porn, it's not like, "hey this other site has this exact model that I want to see getting fucked the way I wanna see it for $10 less".
JMO though, I don't promote mainstream porn, only unique fetishes.