If you book directly with a porn star,  it is likely that the cost will be less.  That's because the agency's tack on their own fees - after all, they deserve some money for handling the booking/making the arrangements.  However, there are porn stars out there who will charge you the same amount as you paid through the agency because they figure if you can afford it, you can pay it directly to them and they will make more money off you in the long term.  Or they just figure that you don't know that the agency takes a cut.  Or one of several other reasons for them charging you the same amount.  They do it because they think they can get away with it.  

As for getting personal contact info to book direct - that's another story.  Some will give out direct contact info, but most won't.  

Some will, some won't.  I met a star in NYC a few years ago, she gave me her personal cell number. Even told me her real name. We would text back in forth all the time. She even called me on my birthday and on the anniversary of my mom's passing. She contacted me and told me she was gonna be in NYC soon and she came to my home in South Jersey. Gave me a discount as I helped her get the train ticket to and from NYC. We went to dinner and everything. We spent 5 hours together and she only charged me for an hour. She was totally down to her.  

I will not say her name. For her privacy reasons. That was 4 years ago and we still text.