I just want to chip in my experience with trial versus no trial (again from an adult dating perspective, not adult).
We had 2.95 for one week which rebilled to 24.95 per month. We decided to raise that to 4.95 for one week and there was almost no difference in signups (so more cash for us). We then got rid of the one-week trial all together and the minimum membership was 24.95
We had very close number of signups, but worth much more
(and yes, the number of initial 24.95 was now making more than the trial + those who did renew after one week at 24.95...)
I think basically what it comes down to, is many surfers will go for the cheapest choice available. If you eliminate that choice, many will still signups. Thinking 'we will get way more signups at $5 than $25' just wasn't the case, atleast for us
Then again, with adult you have WAY more competition, so the surfer might say 'this site is too expensive, let me go find a cheap one'.