Everything is included.
If you go to Premier, for example, and book a 40-minute session, you pay $150 at reception. You go to the room, shower, the girl comes in, and you've got 40 minutes. If you want to upgrade your session with extras, you might negotiate with the girl, and she might decline, but if you're with one of the liberal ones, it'll typically be $100 for FS. If you don't discuss the amount in advance, give her $100 and say thank you very much.
If you go to see one of the Sassy Angels girl, you can book 60 minutes. Put $250 in an envelope. You'll meet her at a condo. Once you go upstairs and knock on the door, she'll greet you and bring you in. After a brief introduction, head to the bathroom for a quick shower - hand her the envelope before you go in. Come out with your towel and the fun begins. There's no negotiating for extras - they're part of your service. Now your shower time is included in your session time, so don't waste too much time in there! But you do end up with a little more time than you do at Premier, and you've got a bed instead of a squeaky table with a towel on it, and they do have mirrors around (I love that - I manage to look at her and ignore myself when I look). The bed is really nice to have.
So a FS session at Premier is usually $250 for 40 minutes plus shower time, although getting a FS session is not a sure thing. A session with an Angel is also $250, and FS is a sure thing, and you get 60 minutes which includes your shower time. You do not have to tip on top of the fee, although of course you may choose to do so. I brought small gifts to Arya.
Some people on the board will tell you that the girls at Premier are beyond compare and most SPs can't touch them. I have only met one Sassy Angel and she was fantastic, clearly on par with the ones I've met at Premier. There is a lot less intel on the women at the escort agencies. That just adds to the suspense. These girls are all hired for a good reason. They are good at what they do. It is likely that there are some that just don't suit some customers, but that's true in any spa as well.
I sense that you are intrigued but hesitant. I hope this puts your mind at ease. You will have a good time. In my opinion, if you want a FS session, this is the way to go. I know that Premier has a lot of outstanding attendants, and it's really easy to want to have sex with one of them, but Sassy and Top Drawer and Roommates also have some outstanding looking young and talented women of the same class, very much hidden gems compared to the ones discussed over and over here. So unless you have your mind set on a particular Premier attendant, go through the profiles on those site linked above and find the one that calls out to you. (I'm well known for a sweet tooth for chocolate, and Arya at Sassy Angels definitely satisfies that crave. She's the only one I have seen so far.)