Tryst is legit, and the ladies are not cheap. $1500 USD an hour and up in a lot of cases, upwards to $3-5K for very top talent. Many do offer 1 hour dates, some want 2 or 3 hour minimums. It's a bit hilarious when a lady states she doesn't escort, but her profile is up on those sites. Just because she's a porn star, don't expect your session to look like a porn movie. Recent clear test results are often required, and many reviews have stated the ladies mostly tread on their reputations and don't offer a great level of service. They also have makeup artists and hair stylists before a scene is shot, which doesn't happen if they are coming to your hotel room in Vegas or New York. Checking reviews is a must if you going to drop big dollars.
Lourdes is the other legit one, most of the other porn star escorts ads are scam, especially on EROS.