This is a tough question to answer and I've asked myself the same thing several times. After much contemplating, because of the day and age we live and that consumers of porn - in all sexual orientations and niches - have come to expect the moon, the stars and the entire universe for next to nothing, 30 videos would be the minimum in my opinion. However, the site most probably should also offer video feeds and in some cases, access to more sites. When you look at the competition and what they're offering for $20-$30 per month, that about sums it up.

Best of luck with your endeavors. Sincerely.